In order to get this trophy, you need to collect the full extent of the King's wardrobe. Now, you can't buy all of the King's wardrobe all at once, they appear a few items at a time as you progress through the game.
Occasionally items will go on sale, it is advised to always buy items when they are on-sale. Now there is a chance that the King will ask for an item when he sees it appear in the shop. He gives you several actual days to acquire the funds to buy the item. But it is almost always a good idea to buy the item the King asks for because he will always give you a reward (of candy) for buying it. You won't get all of your money back, but it will be better than nothing.
There are 35 items in total for this trophy.
* From what I noticed in my game, you must buy each complete set before the next set appears.
Dandy Set:
Dandy Hat - 60
Dandy Clothes - 140
Dandy Cape - 60
Dandy Tummy Wrap - 60
Dandy Glasses - 80
Sweets Set:
Triple Soft Serve - 180
Melon Tasting Suit - 330
Bride's Cape - 180
Candy Ribbon - 180
Aurora Vision - 230
Bumblebee Set:
Poison Needle Cap - 450
Beekeeper Suit - 850
Wasp Nest - 450
Bellyband - 450
Hornet - 600
Kabuki Set:
Shachihoko - 800
Classic Japanese Suit - 1300
Good Luck Cape - 800
Ceremonious Rope - 800
Kabuki Eye - 900
Kingly Set:
Imitation Head - 1000
Mysterious Stockings - 1800
Divine 'Thing' - 1000
Grinning Sun - 1000
Slithers - 1200
Space Set:
Object from the Future: 1400
Futuristic Suit - 2220
Perspective - 1400
Aluminum Bellyband - 1400
Pearls - 1600
Ramen Set:
Ramen - 1700
Ramen Stockings - 2700
BBQ Pork - 1700
Swirly Belt - 1700
Naruto Glasses - 1900