you need to buy all of the stuff where its cheapest and sell i at the dearest islands then you will get money and be able to buy the biggest boat - eventually!
you have to get doubloons by trading grain silk medicine and spice (go around all of the islands on skullduggery)
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"
go around the islands and trade stuff with then
go to all of the islands and talk to everybody there
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)
The island before it is Steamworks and the one after it is Cryptids. On the newest island map in 2013, it is in the 2nd oldest group of islands, next to Skullduggery.
Once i went to one of the islands and somehow got a new player
sell and trade with other islands (on one island what ever is cheaper on one island is worth more than the next ).
The 6th outlying island is hidden until you collect all 5 map pieces (one from each of the trading islands). It only comes into play after you have driven off Captain Crawfish and have the Treasure Location card from the Governor. Travel to Skullduggery and use the bone shovel to dig at the marked location.
You arrive at Fort Ridley, the Main Street island. Above are Dragon Cove and Bouffant Bay. To the right is Parrot Port. At the bottom left and right are Pirate Outpost and Golden Harbor. Once you have collected a map piece from each of the 5 islands, the 6th outlying island (Skullduggery) will appear near the Pirate Outpost.
I think you go on Skullduggery and there is a secret island that appears on the map after all five pieces are assembled.
Parrot Port- it is the island to the immediate right of Fort Ridley