From the start of the game, use Pilfer Gil to get as much money as possible and try not to buy any items/accessories. Rescue O'aka from the Al Bhed in Macalania Woods (Ch. 1) and corner him in the southeast section of Macalania. Agree to help him and pay off his debt by the end of Chapter 2 (100,000 gil!). When the debt is paid off, he'll have items at a cost cheaper than what you can sell them for. Buy 99 of each item he has (Potion, Hi-Potion, Phoenix Down, Antidote, Eye Drops, Echo Screen, Soft, and Holy Water) and sell all of it to the Gullstore just across from O'aka. Repeat for as much money as you want; each time you buy and sell items you'll profit 16,830 gil!
Added by: Guest Nov 12th 2010, ID#33314