The civics I USE largely depends on the happiness level of my empire. I play on huge map and leader is qin, finacial. If I'm able to get most happy resources and a few religion in my cities, happiness is not much a problem, then I go with universal suffrage, freespeech, caste system, stateproperty and pacifism. Universal suffrage is easy, its good when you have lots towns and when you have lots towns you have lots gold, with those gold i can hurry production in all my cities, nothing takes more then 3 turns to build, even in the poorest city. Freespeech adds more money and double culture. I only go with caste system if my happiness is high, because the emancipation penalty is very high at emperor level. caste system allows unlimited artist which generate huge culture. State property is a no brainer, I got loads watermill. And pacifism for the double great person point.
I don't really find vassalage and theocracy very important, cause half my army is produced by my military city, barrack+west point+pentagon= level 4 unit right out of the gate. vassalage and theocracy don't change much. If my cottages hasn't fully developped into town, i would go with emancipation, also if happiness is not high, I have to stay with emancipation. And if i'm really low on happiness, I will go free religion too.