Uber noob needs help

Hello! i purchased crusader kings 2 a couple week ago with all of the dlc and expansions that were out. I read up on the game a little and tried my hand at Ireland, and set out to become king. I was finally killed off after like 350 years of only having 3 small provinces in Ireland. Can you guys help me out? I just can not figure out this game. Any pointers, tips, guides, or mods you think are necessary would be greatly appreciated.