As you already said, reload is your friend, especially in the beginning and during war times. If you build a wonder for 20 turns and loose by a few turns, reload and see if you can speed up the production, by using a trade route, or chopping woods for instance. Or if it is hopeless, do not attempt to build it in the first place. You can also try to get the other civ into a war, sometimes they will delay building it.
Yeah, Tabarnak's guide is definitely one of the most helpful guides I have ever seen, because of it's focus on the early game, where I always felt playing sub-optimal (and still am, but way less then before).
In almost every era you probably want to aim for the tech that enhances your science research further (universities, public schools, research labs) first or at least second, and build or buy the buildings in your biggest science cities asap.
Besides Tradition, Rationalism is probably the strongest for beginners. Ideology is very situational, if you have the votes in the WC to make it the world ideology, you can basically choose freely, but if not, you whether go with what the people want, or you might be wasting all the ideology tenets to keep your folks happy.
Keep selling resources and lux to the AI. Especially horses are overrated. I keep selling them to the leading AI, as I think it will hurt them more than benefit. Iron on the other hand I sell to the weakest.
Once the AI knows your capital, sell your embassy for 1 gold per turn.
With your warrior, do not engage barbarians early on, keep exploring. Build scouts (I usually do two) first, find ruins. If you encounter another's civ scout, do not run behind him but go the other way. If you play with random seeds, you can reload the game until you get a ruin that you like. Scouts with advanced weapons are quite fun as they keep ignoring terrain cost. So they can move into woods or on hills and still shoot in one turn.
Do not fear to declare war on another civ in the very early game to steal a worker or a settler. They do not have enough troops to go after you and stealing two+ workers from other civs and one from a city state means you do not have to build them. You can keep the war with the city state going to train your troops a little.
Be always friendly to the UI and do as they tell you. But you can deny to go to war, they will not hold it against you. Open borders are situational, be careful, does not hurt to deny them either when in doubt. In the World Congress, try not to vote against anything. Vote for something that will pass anyways. it will make the AI happy, and even if there is a clear looser (like embargo) they will not hold it against you. If you are up to propose stuff, try to propose things others like. For the-next-host votes, every civ will usually vote for themselves, vote for the one that will be leader anyways, or make someone else leader if you have not enough votes for yourself. This alone sometimes helped me to avoid war. Be careful which city state you ally with and which to protect. it might hurt your relations or your purse if you invest in a city and then have to revoke the protection.
Check your borders on a regular basis, if you see troop movements on your border that means the AI is preparing to strike.
Try to keep (esp the warmongering) civs busy with fighting each other, but do not overdo it. If a Civ starts to eliminate one civ after the other it might become too strong in the end, and you will need to prepare to put an end to it.
You will not be able to build everything in every city, so do not attempt to.
Do not underestimate the power of internal trade routes. If you are behind in science it might be a good idea to do external trade routes for the extra science, but the advantage diminishes as you catch up.
Do not keep your cities in production mode for too long, they will grow too slow, and it will negatively effect you in the long run.
Some domination tips:
Get two horses, two melees and a lot of archers, later artilleries. The game is about range, hitting and not getting hit. A nice naval fleet can be obtained by using privateer and capture enemy ships, that can have a good snowball effect. In one game I build one frigate and one privateer and ended up with an army of 10+ ships.
Try to find another civ that will go to war with you. It will lower your warmongering penalty with them and will distract enemy troops. If possible, ally nearby city states first for further distraction. If the Ai captures it, you can free it for some liberation bonus.
Even though it is tempting, try not to fully eliminate another civ, rather capture/raze all but one city, make peace and let the someone else finish them off. They will happily do so and other civs will hate them for that.
The AI is dumb as hell, and especially when it comes to cities with limited access. The AI might place their range units in front of the city, effectively blocking the access for the melee units, who are then unable to reach it. in those circumstance, make sure to not kill the range units until all melees are dead.
For enemy range units hiding in their cities, use a worker-bait to lure them out.
The AI will happily destroy their melee units against a city instead of withdrawing, if a melee is almost dead anyways and the city is not in risk, choose a target with more health instead.
For range units, get the range promotion first (3xterrain bonus, then range), it will be the only way those units will be of any use later in the game.
The demographics are pretty worthless when it comes to army size. Even if an enemy is supposedly X times stronger than you, they do not know how to use it. Also it contains a lot useless units, like ships in the middle of the ocean, or carriers in general, etc. Atomic bombs are also worth 'a lot' in that statistic I think, but more often then not I have seen the AI drop bombs on empty cities, or even not using them at all. Once an enemy dropped bombs on single city until it was completely destroyed...did not know they can do that until then. Still totally worthless, he could have destroyed a good chunk of my army, but chose to destroy a city, and with that, basically commit suicide.