In my Vandal campaign I marched on Italy, took the entire peninsula, spend a few years re-building and recruiting and facing down rival hordes, then made the march for Spain and north Africa.

I'm a bit of a roleplayer though, and an aggressive and proud beligrent at that so any faction that rubs me the wrong way will be wiped of the map... I actually controlled the whole WRE territory and pieces of Germanian lands in the end because I am so often annoyed by my neighbours ;)