Playing a game on deity right now and I'm totally owning the AI on a large Erebus map.
Find a good place to start (duh), which is easy since a 1st turn settler on a mountain can look quite far. Produce 2-3 thrall minions, then your hero Egrass the Founder. Egrass is a worker unit with the Spring and Scorch spells, giving you instant terraform. Also handy for defense with his 2/4 combat values.
Research Hunting, which allows you to upgrade your Wild Trolls to Troll Hunters. They are like normal Hunters but have a strength of 6/4 and ignore terrain movement cost and can climb mountains.
Use your hunters to find goody huts, civilizations and barbarian cities. Wait until barb cities grow to 2 or higher, then occupy and hold them. Destroy them only if they are too far away or the first ring sucks. Carefully level your hunters and in time you'll even be able to conquer AI cities with them. They can level quit safely by placing them on a mountain next to a barbarian stack.
You can't build your strong units, you have to promote Jotnar citizens to whatever you want, including workers and settlers. Start with at least one worker and get hunters as soon as you researched the tech. Citizens function as workers, too, but they only have a work rate of 60 while workers have 120 which can be further improved as time passes.
You can't produce most units. You have to wait until Jotnar Citizens are born, which upgrade to everything else.
You don't get Adepts. Your first magic unit is the Mage/Skald, which requires Sorcery.
You don't get Disciples. Your first divine unit is the Mout of the Divine, which requires Priesthood. Mouths don't die when they spread religion.
You need money. Lots.
Thralls don't cost you any upkeep and can be sacrificed for a few hammers. When in doubt, build thralls.
Your cities only work the first ring. That means you can neglect culture in the beginning.
Your cities can grow to a max size of 8 no more. Once a city hits 8, check if you can replace your farms for something more useful.
Hope that helps.