I wanted to add this because I had to look EVERYWHERE to find out why my Gachas wouldn't eat to tame up!
Gachas who are in the vacinity of other Gachas (live or dead) sometimes will not eat the things you throw on the ground for them. Go ahead and kill the other Gachas(s) than the one you want to tame harvest the corpse(s), move out of render distance, return and try again.
Gachas who have recently been in combat also will sometimes not eat things thrown on the ground. Kill any hostile creatures in the area, punch the Gachas, move out of render distance, return and try again.
This last bit is just speculation because it needs more testing. I believe metal doorframes may provide less taming effectiveness than other metal structures. I would've gotten a 135 Gacha to lvl 202 with metal walls but using doorframes it tamed at 200.
If you are wanting to tame with the snow owl. You can use the owl’s secondary attack to freeze the owl and use up the stamina. This will force it to eat more and will produce the pellets for taming the gatcha. It also works well once you have it to get higher quality crystal drops from it. Just put the owl in front of the gatcha and then when the owl drops pellets the gatcha will pick it up automatically.
To raise baby stone behemoth gates give 400 to food they eat it by the stack. Berries work but eat eats a ton and I'm talking about over 2-3k in weight of berries in its inventory and it ate all within an hour. Also do t try the adding to inventory by hand, drop the stack. It will only pick up stacks if its standing not sitting.