Stiltzkin is a Moogle who appears at various points of the game beginning in Alexandria. He sells you a collection of items each time you meet with him at a discount price and the items get progressively better as you proceed through the game.
Stiltzkin uses the funds to allow him to continue his journey across Gaia, but he will show up at each location regardless of whether you purchase the group of items.
The final purchase that you can make from Stiltzkin will net you a 
Ribbon but only if you purchase all of the items at each opportunity.
Stiltzkin can be found in each of the following locations listed below. Click on the location to be taken to that section of the strategy guide:
The first encounter with Stiltzkin (aside from receiving a letter from him in Alexandria) is in the courtyard of Uptown Burmecia. Open the treasure chest at the back of the room and he will appear.
Cost: 333 gil
Items: 
Soft, 
Hi-Potion, 
Ether
The second meeting with Stiltzkin is on the upper floor of the Inn in Cleyra. You cannot return to Cleyra after this section of the game, so make sure you stop by before proceeding with the story beyond Disc 2.
Cost: 444 gil
Items: Ether, Hi-Potion, 
Phoenix Pinion
The third visit with Stiltzkin is along the pathway in Fossil Roo. This meeting is hard to miss.
Cost: 555 gil
Items: Phoenix Pinion, 
Remedy, Ether
The fourth visit with Stiltzkin is along the Conde Petie Mountain Path and can’t be missed.
Cost: 666 gil
Items: 
Magic Tag, 
Tent, Ether
The fifth visit with Stiltzkin is at the beginning of Disc 3 during a visit to Alexandria inside the Steeple.
Cost: 777 gil
Items: Phoenix Pinion, Hi-Potion, 
Elixir
The sixth visit with Stiltzkin is in one of the rooms inside Oeilvert part way through the quest.
Cost: 888 gil
Items: Hi-Potion, 
Emerald, Elixir
The seventh visit with Stiltzkin in the storage room of Bran Bal. You have to enter the room, leave, and then re-enter the room.
Cost: 2,222 gil
Items: 
Diamond, Ether, Elixir
The final visit with Stiltzkin in back in Alexandria in Disc 4.
Cost: 5,555 gil
Items: 
Moonstone, 
Ruby, Elixir
Over the Moon
In order to obtain the Over the Moon Trophy you will need to obtain all four Moonstones that are available in the game. This means that you will have to complete this side quest in order to obtain the trophy.
The final reward that you will receive from Stiltzkin (if you purchase all of items that he sells) is a Ribbon. There is no way to go back and revisit some of the encounters with Stiltzkin throughout the game so make sure that you purchase all of the available items from him.
Driving the Hard Bargain
You must purchase all of the available items from Stiltzkin each time he appears in order to obtain the Driving the Hard Bargain Trophy. This is a missable trophy as you cannot return to some sections of the game in order to buy items that you have missed.
