well you need to beat other ships to gain not only doubloons but cargo as well. this might depend on your ship if you have the first ship then it might be hard to beat other ships but you know, you can trade cargo for money and you can roam the seas for cargo and money to sell, sorry but i have not found any cheat for this island yet!
You can get doubloons by sinking other ships, monsters and by selling cargo.
yes you have to keep selling cargo and trashing boats the boats get you more cargo and for more go to YouTube type in poptropica how to get doubloons they have alot of videos thank me when you see it
Buy boats with doubloons
This is a long process (at best 3 to 5 hours of play). There are no shortcuts.(see related question)
keep trading
you can hire a cargo master who increases your cargo storage for 15 000 doubloons & a shipwright who fixes your ship without having to go to port for 20 000 doubloons and a cannon-er to reload your cannons twice as fast for 30 000 doubloons
Earn 500,000 doubloons then get a loan at Golden Harbor at the bank .Or you can as many as Grains as you can then sell it at Pirate Outpost until you get 1,000,000 doubloons.
the cannoneer is 20,000 doubloons.
you have to get doubloons by trading grain silk medicine and spice (go around all of the islands on skullduggery)
You can get more doubloons on skullduggery by finding random pieces of cargo around the sea or by selling your items (Grain, spices, silk and medicine) another way to get money is to get a loan from the loan officer on the golden harbor good luck .
it costs 20,000 doubloons
search this on youtube;GET MILLIONS OF DOUBLOONS IN POPTROPICANA ! REALREALREALThen watch.