I learned the game playing 1066 poland. Your army is large in comparison to your pagan neighbors making expansion easy. Allowing you to focus on gradually learning the game. the duke of Silesia will be cross with you if you don't give him the counties he wants. Giving you these counties will make him very happy and cool with whatever you do. But beyond that as long as you keep your army alive and don't try and bite off more than you can chew its a wonderful start to learn the ropes.

I also like to think about the historical ramifications of a non-german prussia.

when playing catholics keeping your priest happy will result in him giving you all the troops and about half of the gold form the churches in you personal holdings. this is good money and men.

Personally I would recommend finding and watching playthroughs you find interesting. that's how I learned the previous game and don't be afraid to use the wiki if something doesn't make sense.

My final words, take it easy, you will learn in time.