First, go to Oakvale. Then, go to the guy the sells ITEMS, not weapons, and buy all his emeralds(Click on the "Buy all # emeralds). After you buy them all, he will have zero so he will pay more for than he sold them for, but don't sell them. Check until the next delivery and wait(sleep)until the guy delivers them. After the store owner gets his delivery, buy all his emeralds(click on the "Buy all # emeralds"). Then sell all your emeralds(click on "Sell al # emeralds"). You will be selling each one for more than you bought it. Repeat these steps as much as you want.