I started out as the King of West Francia, who has claims on nearly all adjacent Kingdoms. All of the Rulers in the area are of the same dynasty, so it was easy to unite Charlemagne's old realm through succession and pressing claims. I married off some relatives to the Byzantine Empire, and eventually one of my rulers had a weak claim which I pressed during a succession war. After that, I took Jerusalem through a crusade, I took Venice by fabricating a claim, I took Croatia and Rome (owned by the pope) by pressing de jure claims, and I took Antioch, Alexandria, and Tunis through holy wars.

how? did you get good rulers to do so?