At the start of the game, leave Lord British's Castle and go to Iolio's Bows (in Britain) and sell everything that you own. Go next door to the Items salesman and purchase as many gems as you can carry. Sell them at Iolio's Bows, then repeat the process eight to nine times. At first, it will appear that all your money has been lost. However, you will eventually gain a large amount of money.