What do I even do in this game?
It's really up to you how you want to play the game, but the more creative you are the more fun you will have. It's a social game so most things will revolve around other players, but it is possible to enjoy the game solo. Here are some of the things that some players do but this is by no means an exhaustive list:
Make a Kingdom
Build a kickass city
Become Pope
Create a Trade Empire
Become a Union President and launch a boycott
Conquer people for no fuckin' reason
Roleplay in royal courts and try to ERP
Literally do nothing but write shitpost tickets every day
Run around and rob people
If you mostly just want to build, I'd recommend the Territorial Path
If you want to build and be involved in politics, I'd recommend the Temporal Path
If you want to build but don't want to play very often, I'd recommend the Spiritual Path
Unfortunately, it's pretty hard to accomplish most goals without building something. It becomes much easier with roleplay and diplomacy. Players can bestow titles which grants you access to their cities or armies, without having to build anything.