A "sly way" is go to SW to spirit island and save. Then go to the trader ship that will be a bit more SW from there and go in a defete the monters and talk to the guy there, he'll give you some tresures, between 2-4 then exit the ship and save. Turn off your ds go into settings and put the date up by ne day. Then go back to him and do it again and he'll give you more. I did this and got like 20+ tresures from him and made 9999 in like an hour after selling them.