I know most about the history of England and Scotland... and I am a little scottish, so my first playthrough I become the world's richest man and vassal of Scotland.
Updating to v0.15 and importing my old character, I'm busy experimenting. A vassal of the Tuscan league right now, but that's kinda boring. I am trying to find a new "favorite" to join, befriend everyone around me, then become king. Last time I tried that (as the vassal of Scotland) I was to spread out and started on my own to soon. Ended up having both England and Scotland trying to kill me, with my lands spread all across the island.
If only the entire map was filled, then I would either go conquer Greece, Jeruselem, or Egypt and go from there. My plan now is to just re-forge the Roman Empire.