I always attack Carthage and Numidia following senate instructions wiping them out first. Afterwards I always sent a ship across the sea to grab Crete and from there I just followed the Senate's missions against the factions over in the Eastern regions. It made me nice and rich I can tell you - 20,000 denarii coming in per turn. However I did get richer as the Julii - somehow my treasury became 1,000,000 after a total conquest of Greece off of the Brutii with 50,000 coming in per turn! Cheers!