Most Important Ports?

For me, you should get Antwerp, near British Isles. It controls all the trade near Scandinavia.

For the West Mediterrenean, your priority should be Genoa and Marseille, as these two cities mostly operate the trade there. Then you can think of getting Ajaccio and Cagliari. If you develop these cities, they can turn out monster-trade cities. Then you can get Florence, Rome, Toulouse and Palermo, but these cities are not much important as others.

For East Mediterrenean, I'm not very good at it. You MUST get Venice, I got 50.000 from sacking it and it gives me 4500 florins by turn :dizzy2: You can get Jerusalem, Acre, Nicosia, as they seem to have lots of trade routes.

In my games, Antioch is always the wealthiest in the Mediterranean.

Antioch, Constantinople, Nicaea, Thessalonia, Alexandria are all major ports as well. In the Baltic, Stockholm and Novgorod as well as Arhus can turn into nice ports.

In the end, just conquer as much as you can and make sure to build ports in every coastal territory. An absolute must build building is merchant's wharf. It's ridiculously good at boosting income.