Hey this thread is a compilation of the most powerful combinations of religious beliefs for Byzantium. In short Byzantium allows you to choose an extra religious belief which does give the player the opportunity to create some unique religions with very powerful benefits. If I miss anything please add your thoughts.
1) Sacred Sites Culture Victory
Basically Sacred Sites produces 2 tourism for each religious building. This is perhaps the most popular of the Byzantium victory strategies and some players have managed to get cultural victories ridiculously early. However this strategy is very unlikely to work at the higher difficulties but the bonus to tourism is still very helpful in giving you a headstart towards a cultural victory.
Pantheon: Faith or Faith/Culture (you have a lot of religious buildings to purchase so you will need lots of faith)
Followers including Bonus: Cathedrals, Pagoda's, Monasteries
Founder: Tithe or Pilgrimage (for extra faith) or World Church (for extra culture)
Enhancer: Probably Itinerant Preachers or Religious Texts so you don't need to spend too much faith spreading your religion to your cities. Holy Order is another good choice as it gives you more control over what cities will receive your religion. Messiah is another choice you could consider if you have a lot of distance between your rival religions as you can plant the prophets for Holy Sites.
Reformation: Sacred Sites
If you build the Great Mosque of Djenne, with the beliefs above the capital can get a free Mosque so that will be 8 tourism in the capital with all 4 religious buildings. However any combination of the three religious buildings for follower beliefs will work. Ideally wait until you get the Mandate of Heaven Policy before you start buying buildings so to get the discount. You certainly want to build a wide empire and the religious buildings will provide happiness, faith and culture to offset the penalties of owning many cities as well as maximising tourism.
Be careful with spreading your religion as other civs will get access to all these religious buildings making them quite powerful as well as the tourism. At higher difficulties you will probably need to pick an enhancer that helps keep your religious pressure up to prevent your cities from converting. Holy Order is another option as it will allow you to buy missionaries and inquisitors at cheap prices so you can easily keep your cities following your religion.
I should note as well that when you enter the Renaissance era and then the Industrial era the price of purchasing religious buildings and missionaries & inquisitors increases a lot so you should try and have most of your religious purchases done by the time you finish the medieval era. Consider delaying entering the renaissance era if you are short on faith.
2) Holy Site & Wonder Culture Victory
This is an alternative culture victory strategy
Pantheon: Faith or Faith/Culture, Food pantheon if the benefits are worth it and you can get faith quickly from another source.
Follower: Divine Inspiration (Faith is directed into Great Prophets and other Great People so there is little faith to be spent on missionaries or religious buildings). For the second follower perhaps Feed the World or Swords into Ploughshares or Pagoda's. Basically whatever helps with building Wonders and staying Tall.
Founder: Tithe
Bonus: Religious Community (this will provide your cities with a great increase to production which is fantastic for Wonder building)
Enhancer: Messiah
Reformation: To the Glory of God
This strategy will work for culture victories by focusing on Wonders and on tourism from tiles. You will need to fill out Piety to get the bonuses from Holy Sites. However the advantage with this strategy is you don't need to rush Piety as you can't use your reformation belief until the industrial age and I don't think the AIs really favor it. So you can don't need to finish Piety immediately as opposed to Sacred Sites which you can't risk an AI beating you to. I favour the Liberty tree as the Reformation belief will give you access to Engineers in the Industrial era. The other advantage is it gives you access to Great Scientists so even if you fall behind scientifically you won't need to fill out the entire Rationalism tree.
You want to build as many Wonders as possible and I would consider Stonehenge as essential to maximise faith. Temple of Artemis is another good option. Basically all the early Wonders that give you Great Engineer Points are good as the more Engineers you get the more Wonders you can rush... I also recommend the Oracle as you have 2 ancient era social policy trees to fill out in this strategy before you move to Aesthetics.
You should pick the Freedom ideology to get New Deal for bonuses to Great Person Improvements. If you fill out the Piety tree, the Liberty tree and build Hagia Sophia that can be 3 extra Free Great Prophets. All the Holy Sites should be planted around the capital to generate late game tourism. It can be useful planting them in the 3rd ring of tiles so a nearby city can work them if you need the capital to prioritize on food or production tiles.
You definitely want to get Cultural Heritage Sites and Historical Monuments from the World Council to boost Wonders and Great Person Tiles.
If you can pass your religion in the World Council resolution than this strategy will net you an enormous amount of tourism. As your religion will be more restricted to your Civ in this strategy this might be difficult but perhaps you can try using your diplomats.
3) Global Religion
This strategy will produce a religion that can easily cover the world and will work with whatever victory strategy you choose. Basically it will give you massive religious spread. You should focus on building tall cities to and getting the Grand Temple ASAP to maximise religious pressure. You probably want to pass your religion as a 'World Religion' in the World Council which will give you benefits towards Culture or Diplomatic Victories. A faster religious spread will also give you even more benefits from your Founder belief.
Shared religions can work well with diplomacy and can even buy you friends with warmongers like Shaka. Shared religion modifiers also help towards Culture Victories. If a Citystate follows your religion its influence will drop more slowly.
I recommend choosing Tradition and building the Temple of Artemis and Hanging Gardens in the Capital to get massive growth. Keep as many 'We love the king days' in the the capital & other cities as possible. Basically the bigger your capital is the more religious pressure the Holy City will exert. Trade routes should be used either to help spread your religion or in the early game to quickly grow your capital.
Pantheon: Whatever
Follower: Something that you think will either benefit you over the other Civs or will benefit the spread of your religion. Perhaps Feed the World or Swords into Ploughshares. The faster that cities with your religion grow the more pressure they will exert.
Founder: Tithes - clearly the best of the Founder beliefs for a super religion. This will net you heaps of gold so you can rush purchase buildings and units or buy CityStates.
Bonus: Itinerant Preachers
Enhancer: Religious Texts
Reformation: Unity of the Prophets (very good to counter other religions spreading)
4) Patriot Religion
I call this one patriot as the benefits will mostly flow back to your Civ. It's nothing really special except that it chooses two Founder beliefs (using the bonus). Byzantium is the only Civilization that can choose 2 founder beliefs. And as founders only benefit your Civ, this type of religion will benefit you the most while still focusing heavily on religious spread so the more your religion spreads to other Civilization's cities the more you gain. Without a specific victory strategy this is probably the best type of religion to choose as it will be quite flexible.
Pantheon: Faith, Faith/Culture
Follower: Something that you think will benefit you over the other Civs, Mosques are good for extra faith generation
Bonus: Church Property or whatever Founder you choose
Founder: Tithes
Enhancer: Messiah for Great Prophet bombing of other Civs new religions or something to help missionaries or passive pressure.
Reformation: Unity of the Prophets (very good to counter other religions spreading, so other Civs support your 2 founder beliefs)
5) CityState Alliances and Diplomatic Victory
This religion focuses on improving relations with CityStates
Pantheon: Whatever
Follower: Whatever
Bonus: Tithes (to buy Citystates)
Founder: Papal Primacy
Enhancer: Itinerant Preachers or Religious Unity if you have heaps of CityStates nearby you can stay friends with. Missionary Zeal or Messiah or Holy Order are also options for helping you convert CityStates. Just pick whatever you think will work the best.
Reformation: Charitable Missions (extra influence from gold gifts to CityStates). I have tried this with Underground sect but unfortunately the amount of pressure that spies exert seems insignificant so do not use that belief which is a shame because the concept is really interesting as you often keep spies in Citystates to rig elections and perform coups.
6) Science Victory
This is a mixture of beliefs that will work with Interfaith dialogue by allowing you to produce heaps of missionaries and generally maximise science. You should try and build the Great Mosque of Djenne and if possible Borobudur afterwards so you get huge benefits to missionaries.
Pantheon: Messenger of the Gods or Faith belief (I would choose faith as it will allow you to buy more missionaries)
Follower: Something that helps with faith. Probably Pagoda's as the extra happiness really helps with growing large cities to support science.
Bonus: Pilgrimage or Holy Order
Founder: Interfaith Dialogue
Enhancer: Missionary Zeal
Reformation: Evangelism for even better missonaries or Jesuit Education
7) Religious War for Domination Victories
This is another one I haven't tried but I imagine it could make for some interesting games. I'm a little unsure of what the best combination of beliefs would be but the idea is that you want to pick religious beliefs that benefit you in war. For 2 the enhancer beliefs you will need to aggressively spread your religion to neighbouring cities before you conquer them and that can use up a lot of your faith which you probably want to keep for Holy Warriors. Perhaps someone can way in on how this would be best executed.
For the pantheon I suggest choosing the setting Raging Barbs so you can farm barbs for faith. Defender of the Faith is likely to be very handy as you will likely attract a lot of hatred from your neighbours so if you capture an enemy city in their territory, spread this belief to the city and it will help you clear out enemies nearby until you're ready to move onto the next city. I imagine this would work well with Just War if you're able to convert these cities before you attack them.
Pantheon: God of War
Followers: Holy Warriors and Pagoda's (Pagoda's are great for warmongering as the happiness and culture definitely benefit your Civ)
Bonus: Defender of the Faith
Founder: Tithe, Pilgrimmage or Ceremonial Burial depending on whether you value Gold, Faith or Happiness the most - basically whatever is in shortest supply which for warmongering is often gold and happiness.
Enhancer: Just War
Reformation: Religious Fervor
1) Sacred Sites Culture Victory
Basically Sacred Sites produces 2 tourism for each religious building. This is perhaps the most popular of the Byzantium victory strategies and some players have managed to get cultural victories ridiculously early. However this strategy is very unlikely to work at the higher difficulties but the bonus to tourism is still very helpful in giving you a headstart towards a cultural victory.
Pantheon: Faith or Faith/Culture (you have a lot of religious buildings to purchase so you will need lots of faith)
Followers including Bonus: Cathedrals, Pagoda's, Monasteries
Founder: Tithe or Pilgrimage (for extra faith) or World Church (for extra culture)
Enhancer: Probably Itinerant Preachers or Religious Texts so you don't need to spend too much faith spreading your religion to your cities. Holy Order is another good choice as it gives you more control over what cities will receive your religion. Messiah is another choice you could consider if you have a lot of distance between your rival religions as you can plant the prophets for Holy Sites.
Reformation: Sacred Sites
If you build the Great Mosque of Djenne, with the beliefs above the capital can get a free Mosque so that will be 8 tourism in the capital with all 4 religious buildings. However any combination of the three religious buildings for follower beliefs will work. Ideally wait until you get the Mandate of Heaven Policy before you start buying buildings so to get the discount. You certainly want to build a wide empire and the religious buildings will provide happiness, faith and culture to offset the penalties of owning many cities as well as maximising tourism.
Be careful with spreading your religion as other civs will get access to all these religious buildings making them quite powerful as well as the tourism. At higher difficulties you will probably need to pick an enhancer that helps keep your religious pressure up to prevent your cities from converting. Holy Order is another option as it will allow you to buy missionaries and inquisitors at cheap prices so you can easily keep your cities following your religion.
I should note as well that when you enter the Renaissance era and then the Industrial era the price of purchasing religious buildings and missionaries & inquisitors increases a lot so you should try and have most of your religious purchases done by the time you finish the medieval era. Consider delaying entering the renaissance era if you are short on faith.
2) Holy Site & Wonder Culture Victory
This is an alternative culture victory strategy
Pantheon: Faith or Faith/Culture, Food pantheon if the benefits are worth it and you can get faith quickly from another source.
Follower: Divine Inspiration (Faith is directed into Great Prophets and other Great People so there is little faith to be spent on missionaries or religious buildings). For the second follower perhaps Feed the World or Swords into Ploughshares or Pagoda's. Basically whatever helps with building Wonders and staying Tall.
Founder: Tithe
Bonus: Religious Community (this will provide your cities with a great increase to production which is fantastic for Wonder building)
Enhancer: Messiah
Reformation: To the Glory of God
This strategy will work for culture victories by focusing on Wonders and on tourism from tiles. You will need to fill out Piety to get the bonuses from Holy Sites. However the advantage with this strategy is you don't need to rush Piety as you can't use your reformation belief until the industrial age and I don't think the AIs really favor it. So you can don't need to finish Piety immediately as opposed to Sacred Sites which you can't risk an AI beating you to. I favour the Liberty tree as the Reformation belief will give you access to Engineers in the Industrial era. The other advantage is it gives you access to Great Scientists so even if you fall behind scientifically you won't need to fill out the entire Rationalism tree.
You want to build as many Wonders as possible and I would consider Stonehenge as essential to maximise faith. Temple of Artemis is another good option. Basically all the early Wonders that give you Great Engineer Points are good as the more Engineers you get the more Wonders you can rush... I also recommend the Oracle as you have 2 ancient era social policy trees to fill out in this strategy before you move to Aesthetics.
You should pick the Freedom ideology to get New Deal for bonuses to Great Person Improvements. If you fill out the Piety tree, the Liberty tree and build Hagia Sophia that can be 3 extra Free Great Prophets. All the Holy Sites should be planted around the capital to generate late game tourism. It can be useful planting them in the 3rd ring of tiles so a nearby city can work them if you need the capital to prioritize on food or production tiles.
You definitely want to get Cultural Heritage Sites and Historical Monuments from the World Council to boost Wonders and Great Person Tiles.
If you can pass your religion in the World Council resolution than this strategy will net you an enormous amount of tourism. As your religion will be more restricted to your Civ in this strategy this might be difficult but perhaps you can try using your diplomats.
3) Global Religion
This strategy will produce a religion that can easily cover the world and will work with whatever victory strategy you choose. Basically it will give you massive religious spread. You should focus on building tall cities to and getting the Grand Temple ASAP to maximise religious pressure. You probably want to pass your religion as a 'World Religion' in the World Council which will give you benefits towards Culture or Diplomatic Victories. A faster religious spread will also give you even more benefits from your Founder belief.
Shared religions can work well with diplomacy and can even buy you friends with warmongers like Shaka. Shared religion modifiers also help towards Culture Victories. If a Citystate follows your religion its influence will drop more slowly.
I recommend choosing Tradition and building the Temple of Artemis and Hanging Gardens in the Capital to get massive growth. Keep as many 'We love the king days' in the the capital & other cities as possible. Basically the bigger your capital is the more religious pressure the Holy City will exert. Trade routes should be used either to help spread your religion or in the early game to quickly grow your capital.
Pantheon: Whatever
Follower: Something that you think will either benefit you over the other Civs or will benefit the spread of your religion. Perhaps Feed the World or Swords into Ploughshares. The faster that cities with your religion grow the more pressure they will exert.
Founder: Tithes - clearly the best of the Founder beliefs for a super religion. This will net you heaps of gold so you can rush purchase buildings and units or buy CityStates.
Bonus: Itinerant Preachers
Enhancer: Religious Texts
Reformation: Unity of the Prophets (very good to counter other religions spreading)
4) Patriot Religion
I call this one patriot as the benefits will mostly flow back to your Civ. It's nothing really special except that it chooses two Founder beliefs (using the bonus). Byzantium is the only Civilization that can choose 2 founder beliefs. And as founders only benefit your Civ, this type of religion will benefit you the most while still focusing heavily on religious spread so the more your religion spreads to other Civilization's cities the more you gain. Without a specific victory strategy this is probably the best type of religion to choose as it will be quite flexible.
Pantheon: Faith, Faith/Culture
Follower: Something that you think will benefit you over the other Civs, Mosques are good for extra faith generation
Bonus: Church Property or whatever Founder you choose
Founder: Tithes
Enhancer: Messiah for Great Prophet bombing of other Civs new religions or something to help missionaries or passive pressure.
Reformation: Unity of the Prophets (very good to counter other religions spreading, so other Civs support your 2 founder beliefs)
5) CityState Alliances and Diplomatic Victory
This religion focuses on improving relations with CityStates
Pantheon: Whatever
Follower: Whatever
Bonus: Tithes (to buy Citystates)
Founder: Papal Primacy
Enhancer: Itinerant Preachers or Religious Unity if you have heaps of CityStates nearby you can stay friends with. Missionary Zeal or Messiah or Holy Order are also options for helping you convert CityStates. Just pick whatever you think will work the best.
Reformation: Charitable Missions (extra influence from gold gifts to CityStates). I have tried this with Underground sect but unfortunately the amount of pressure that spies exert seems insignificant so do not use that belief which is a shame because the concept is really interesting as you often keep spies in Citystates to rig elections and perform coups.
6) Science Victory
This is a mixture of beliefs that will work with Interfaith dialogue by allowing you to produce heaps of missionaries and generally maximise science. You should try and build the Great Mosque of Djenne and if possible Borobudur afterwards so you get huge benefits to missionaries.
Pantheon: Messenger of the Gods or Faith belief (I would choose faith as it will allow you to buy more missionaries)
Follower: Something that helps with faith. Probably Pagoda's as the extra happiness really helps with growing large cities to support science.
Bonus: Pilgrimage or Holy Order
Founder: Interfaith Dialogue
Enhancer: Missionary Zeal
Reformation: Evangelism for even better missonaries or Jesuit Education
7) Religious War for Domination Victories
This is another one I haven't tried but I imagine it could make for some interesting games. I'm a little unsure of what the best combination of beliefs would be but the idea is that you want to pick religious beliefs that benefit you in war. For 2 the enhancer beliefs you will need to aggressively spread your religion to neighbouring cities before you conquer them and that can use up a lot of your faith which you probably want to keep for Holy Warriors. Perhaps someone can way in on how this would be best executed.
For the pantheon I suggest choosing the setting Raging Barbs so you can farm barbs for faith. Defender of the Faith is likely to be very handy as you will likely attract a lot of hatred from your neighbours so if you capture an enemy city in their territory, spread this belief to the city and it will help you clear out enemies nearby until you're ready to move onto the next city. I imagine this would work well with Just War if you're able to convert these cities before you attack them.
Pantheon: God of War
Followers: Holy Warriors and Pagoda's (Pagoda's are great for warmongering as the happiness and culture definitely benefit your Civ)
Bonus: Defender of the Faith
Founder: Tithe, Pilgrimmage or Ceremonial Burial depending on whether you value Gold, Faith or Happiness the most - basically whatever is in shortest supply which for warmongering is often gold and happiness.
Enhancer: Just War
Reformation: Religious Fervor
from Desert tiles), One with Nature (+4 
)
