To tame a Gacha, note that the values are represented in stacks of ten, so "Metal Structures(10)" indicates 30. The Gacha has an appetite for any weaponry or armor, and the quantity needed adjusts based on the item's resource value - a Shotgun, for instance, equates to 5 Bows or 10 Slingshots. The resource demands for taming a Gacha rise only marginally with its level; the difference between a level 1 and level 150 is minimal. Bear in mind that the taming effectiveness given is approximate.

Passive: You need to tame it while the Gacha is awake.