It requires 5 Power Gems, 5 Lucid gems, 5 Thunder Gems, 3 Gales, and 3 Mystery Goo. Here are where they are found:
POWER GEMS: Dropped by almost every enemy on the Neverland Ship Deck.
LUCID GEMS: Dropped by Wight Night and Gargoyle at Halloweentown.
THUNDER GEMS: Dropped by Screwdrivers and Aquatanks at Atlantica.
GALES: Dropped by every enemy in the room before Final Rest at End of the World.
MYSTERY GOO: Dropped mainly by Black Fungus at: Agrabah, Bazaar; Halloweentown, Moonlight Hill; Hollow Bation, Cell; End of the World, Linked worlds. To get a mystery goo easily, defeat them with Trinity Limit.