It gets tricky if you do not have a steady source of money, and it gets far trickier when you consider diplomacy and overall strategy. Who to ally with, how to maintain those alliances, when to turn on the allies, and how to conquer the enemies without having the entire world against you. I once played a Greek Cities campaign in which everybody except the Gauls, Iberians and Bactrians were at war with me. Even the Armenians were blockading my ports for some reason, even though I did not share any common borders.