@NekuSakuraba: I can give a brief rundown from my playthrough if you'd like. basically you want to get the 10-15 faith points fast its a first come first serve bonus i think. there's 3 stages to religion, first is the pantheon, then the establishment and then an enhancement thing. first stage you get one bonus, every stage after 2. usually from the same list at least for the ones following the first. after you get to establish a baase pantheon you have to accumulate 200 faith points or more for the great prophet. at this point you can choose a religion/rename it. at this point civ is played as it usually is with the exception that every (starting at)200 faith points you can buy a missionary/inquisitor or wait for a prophet. Many of the bonuses are based on how many you can convert so, you need to keep on that. At some point around mid game if you've been converting as many as you can/upgrading your religion you unlock a great person as a buyable unit(i think it has to do with a culture unlock as well, having finished certain trees, i want to say tradtion,rationalism,commerce,honor) via faith points but like everything else with faith points price increases (great person increases by 500 point cost after buying them i believe, great prophets goes if i remember 1000,1200,1300, 1700,2000, etc.) anyhow it seemed to follow my playstyle and unlocked great engineers(id gone down tradition and chose a bonus which gave me +15% productivity on ancient/classical wonders) for me to buy later Merchants because i suppose id completed Mercantilism/passed a threshold. at least its what i noticed. spying is also just sending spies from a list to other places. you don't realy have to touch that since it does the rigging elections/notifying you of moving armies and steals tech automatically.
AI wise, they seem to be a lot more backstabbing in even prince difficulty, an example from my game is spain/washinton attacking me because i was busy finishing arabia. However Washinton instead went and attacked spains undefended capital forcing spain who would have taken my cities to retreat. Barbarians are a lot more common, they spawn a lot, i felt that you cant leave your capital alone too much even at the beginning because barbarians would screw you otherwise.
well thats all i can remember off the top of my head.