I’d say it’s easiest to tame these guys after lvl 61, when you can get a Basilo saddle. Use the Basilo to get a lot of biotoxin and then trap the galli when it stops moving. A one by one by 2 fence trap should suffice. Then just shot the galli in the face with a longneck and there yah go.
If you have a Snow Owl and two people, make sure not to aggro it, and have one person freeze it and while it's frozen have the other person quickly build either high stone walls or two wood walls stacked on top of each other around it. You can use fence foundations to put the walls on top of and can put a wooden door frame on top of a wall on one of the sides so you have a place to jump and shoot at it from.