I guess I got lucky in my campaign, I went for Sardinia and Corsica early on and converted them into cities, then I went durazzo and noticed that no one had managed to conquer florence, tough they did weaken their garisson, at the same time , Venice got excomunicated for completely destroying Milan and I crusaded that fortress above Durazo from them, and Venice and now I conquered Genoa, Milan and Marseille from Venice, I also just landed an invasion force on Iraklion so I managed to ratehr quickly conquer a strong trading empire with soem allready nicely developped cities. Venice only has Dijon left wich I don't intend to take just yet as it's better for me if someone keeps the french and HRE occupied. I think I'll go for the other islands in the mediteranian, and then set out to destroy the moors for Timbuktu's riches, aftr that I'll take on Egypt in a few crusades.

Another thing that helped a bit (tough not extremely much) is the little bit of income from merchants, the ones on your islands are safe and generate some, the 2 sheep recources in Naples grant you a nice little bit of money, and the grain helps the city grow if you have a merchant on it. with all my merchants trading little amounts all together they are generating a bit more then my top city wich is Naples

I have one big standing army (currently laying siege to Iraklion), 2 fully garissoned cities and a grand fleet with 10 fleets in it and I'm still making a profit