Originally Posted by
TheFallenOne
In my experience the fastest way to expand is religious CBs. You don't need to worry about attaining claims and on victory you get all holdings in the contested area, to be distributed as you see fit.
That's what I did in my Sieghardinger game. Work up from count to king of Germany, my Genius heir founds the HRE and conquers Zeeland and Sjaelland. Move capital to Sjaelland, convert to capital religion through decision and instantly enough religious authority to reform Norse paganism. With a bribe here and there I had enough vassal opinion to get most of them to convert right away, those who refused lost their titles one after the other. There were a few vassal's vassals who remained Christian holdouts but they never caused real trouble.
After that I could just swallow up the rest of Italy and the four separate kingdoms in France duchy by duchy until I got bored. Even casually conquered Tunis, gave the title to a son and granted him independence to lower my Threat score. He made king of Africa later all on his own.