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 much oil as you can carry. Sell them at Iolio's Bows. If a single character holds two loads of oil (99 + 99) and sells it all, it will result in 350,000 gold crowns.