To unlocked the King of Bling trophy in Devious Dungeon, you simply need to unlock any Amulet when visiting the merchant. He can be found in the King's hall at the beginning of the game (you'll return here whenever you die) or between every four levels in the game itself.
The first Amulet (Amulet of Will) is only 100 coins, which you should be able to obtain very quickly in the game if you smash all of the objects in each level you come across.