- First, go back to a save file where you have like >4k coins or something (the more the better)
- Then you need to hoard lots of goods (buy them whey they are sold at low prices- as indicated by the green arrows).
- Next, travel to other islands and check their markets (sell mode), if your items can fetch a higher price (higher than their normal prices) then sell them. If not, you can either keep travelling between islands till you find a reasonable price (which might take tons of supplies), OR load your save file, buy the same goods again, and go for a different market (this way you dont have to buy more supplies)
- Repeat the process and profit.
Another thing, lets not touch the pirate coins rn, i think the exchange rate is buggy atm, hopefully it will be fixed in the next patch.