For a low level giga trap it in a circle of stone dinosaur gates, for a high level use metal. The torpor of a giga drops about 200/second so if you stop shooting it it will lose it all. It's possible to solo tame, though the more you have the less time it will take to knock down. You should use darts, always bring a couple extra hundred.
I dare you to raise one!! They are savage if you got two high lvl parents (about lvl 140ish) and you get imprinting on it. The thing will become an adult with about 230% melee and basically one chomp any bronto!!! But on the down side you loose your job and your girlfriend