This is a little trick for a doughtnut-shaped empire.

I've used this cheat with the three roman factions and it worked great. You simply prevent your allies from expanding and keep their strength relatively modest in order to get back at them as soon as you've conquered some 35 regions or so. Cleaning-up the 'brother hood' will be a lot easier and you'll earn enough money to finance the campaigns to get to 50.

The trick:

Send some troops (enough to build a ram in one turn) to siege a settlement as soon as it is undersieged by an allied roman faction (or any allied faction for that mater). If you are slightly lucky, that faction won't attack the turn right after. Call the attack on your turn, but exit the battle screen as soon as the battle is started (I think you don't even have to actually start the battle once you're on the battle screen to get the trick to work). Of course you'll lose the battle, but your ally will have to break its siege and retreat as well. It buys you some time to bring additional troops and take the settlement thereafter.

Using this trick I've limited the Scipii to no additional settlements, the Brutii to Appolonia and the Julii to Segesta. This trick is also usefull to snatch the rebel Athen from the Macedonians early in the game, while playing the Brutii.