A Gacha only eats when it is happy, and another Gacha nearby makes it unhappy, so separate them first: an unhappy one ignores everything you put down. Drop crafted items on the ground from your own inventory and it walks over and swallows them a stack of twenty at a time, so anything that does not stack to twenty is wasting the mouthful. Worth comes from crafting experience rather than tier, so check the table. It refuses eggs, Gacha Crystals and its own saddle.