When I find a giga, I lure it to a location I find easiest to get it stuck. Easiest way to lure it is by placing a dodo or a monkey on the platform on your quetz. It'll register as a land dino and remain aggressive to you. Then get it into a position where if it runs away it gets stuck. I do this with natural traps and solo. Good luck.
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
When taming a giga you want to use 4 gates with a large bear trap. Set down three of the gates in a U shape and shoot the giga from far to aggro it and lead it inside of the trap. Once the bear trap holds the giga in place you have 10 seconds to run and place the fourth gate behind it. I highly recommend taking a throwaway bird, when taming gigas a lot can go wrong.
Make 4 metal dino gates and 1 large bear trap. Place three frames and door into an incomplete square and the large bear trap in the I between them. Lure the Giga into the trap and while its trapped place 4th down to make the square. Then just light it up with tranqs