During your quest, you meet a man who wants to set up a wares shop. If you invest in his start-up expenses, the shop will have different stuff for sale:

1-100 gold - Basic weapons
101-500 gold - Basic skills
501-1000 gold - Better weapons and some skills
1001-2000 gold - Better skills at the cost of more items available
2001-2500 gold - Mega heal kits at lowered prices
2501-3000 gold - Good weapons, items, skills, armor and a mini-game
3001-5000 gold - Great weapons for Lin, poor weapons for Ryu and Nina, and good spells for Nina
5001-10000 gold - Great weapons, skills, spells, stat increasers, armor, items, but no mini-game