I'm glad you liked my suggestion, but not my idea to be honest, it's from board game - Settlers of Catan. if you haven't played it you definitely should try to play it with friends, looks and plays a bit like your game. Meanwhile here's the gist of it: In it you need to use resources to build houses and roads to collect more resources, you also could trade resources with other players on any agreed rate 1-1, 2-1, 1-2, 2-3 and so on. If no one is willing to trade or there is a shortage, you could trade with bank at rate of 4 same resources for any 1 other. You could also build house on predefined general port and get rate of 3-1, or build house on specialized port with rate of 2-1 (specialized ports will only except specific resource, like 2 wheats for any resource you want). There are also many expansion, like sea expansion, where you can build sea routes with ships to get to other islands.
