Collect the indicated number of Gratitude Crystals and bring them to Batreaux to unlock the corresponding bonus.

2 Gold Rupees: 70 Gratitude Crystals
Big Wallet and Cursed Medal (Holds 1,000 Rupees): 30 Gratitude Crystals
Giant Wallet (5,000 Rupee capacity): 50 Gratitude Crystals
Gold Rupee: 40 Gratitude Crystals
Piece of Heart: 10 Gratitude Crystals
The Medium Wallet (500 Rupee capacity): 5 Gratitude Crystals
Tycoon Wallet (9,000 Rupee capacity): 80 Gratitude Crystals