Watched a bit of a Let's Play, which wasnt super applicable for a lot of specific things because they were playing a different government type and had more DLCs than I did at the time, but was very useful in learning how people approached the game on general.

Mostly thought, just playing a lot on Ironman and fucking up a ton. I didn't really get succession until I had lost a lot of land to it, I didn't really get intrigue plots until I tried to imprison a wife and she fled to a foreign court and then successfully killed me, I didn't understand how war worked until I declared war on what I thought to be an easy target only to get crushed by their allies, I didn't quite get vassal management until one time I went crusading and ended up winning all of the former Byzantine Empire and doled it out to random people who ended up revolting against me. Its an investment to learn, took me like 30 hours or so to unite Ireland in the 1066 start (which according to all the things I had read was the easiest thing to do in the game). And a lot of isn't even hard stuff, it's just that there's a lot of stuff to be aware of and it takes awhile to know what exactly to be paying attention to and how to respond. But it's worth it if you like it, because now I have over 300 hours in the game and I haven't even touched some of the major playstyles you can do yet. It's gonna keep me entertained for a long time!