Sell your salvage for doubloons, or buy cargo to transport to a different trading island. For example, buying silk at Dragon Cove, then sailing to Bouffant Bay and selling it for twice the price.
The trading posts, are on each port such as dragon port , the parrot port etc.
Simple. There are trading posts at each island all you have to do is sell and buy things from the post.
You keep trading to get enough money.
keep trading
you have to get doubloons by trading grain silk medicine and spice (go around all of the islands on skullduggery)
You go on the island you want to sell on and go to the trading post
To trade and sell on island on skullduggery island you first must be on one of the 5 islands and walk around you should see a post that says " TRADING POST"
On top of the barrels inbetween the first house and the trading post.
Collect the five map pieces (one on each of the trading islands) and join them to see the sixth island, Skullduggery. Once it appears on the map, you can actually go there, but nothing happens there until the end of the game. (see the related question)
you need a lot of dabaloons. You can get them by finding salavage and trading goods
The shipbuilder (Ship Shape Shipbuilders) is just to the right of the Trading Post.
Go to the hanging ferns. Jump on the 2nd, 3rd, and 1st ferns. Also, do your trading.