Wild Arms

You can get this achievement as soon as you have all three party members. Just use the item duplication trick on your most valuable item and then go sell the stack (save one if you're like me and want to keep one in your inventory). Then go to an ARMS mechanic and just max it out.

The item duplication trick is easy. Get into a fight and have Jack and Rudy use Heal Berries, then with the mage character, switch the berries in the item menu for what you want duplicated and go back and defend. Make sure you only have 1 of the item you want to duplicate.