While playing the game and not in the sanctuary, press Start on controller two, and join the game using a different profile. Have your main character stand next to the second character, and press LB when "Gift" expression appears to be tele-ported to the gift room. There is a blue coin pouch to the right on a pedestal when you enter the gift room. Give all of your current gold to the second character.
Then, exit the sanctuary with the main character. Press Start on controller two to teleport him or her to the sanctuary. To the left, next to your dog's bed/interface, is a gift que. Walk over to it, and press A to display the second character's gifts. Press X to reject the gifts. Press Start on controller two to leave the sanctuary and be tele-ported back to your main character.
When you are near your main character, press Down on controller two to leave the game. Once the second character has left the game, press Start on controller two to rejoin the game and the gifts you rejected should still be there. Duplication Complete; Since the game did not save after you rejected the gifts, they should all be back on the gift shelf. Repeat this as many times as desired. You can also do this with other items, such as flowers, necklaces, etc