You need 2 or 4 behemoth stone gateways to trap the Giga. To lure it I recommend to use an argy and grab a wild dino like a parasaur. Then when the Giga is in your trap make sure to sleep to tame the Giga faster and afterwards knock out the Giga and use prime meat or just normal meat but make to sure to bring it alot because its not work making quetzal kibble. Btw when you sleep the Giga or any dino will instantly eat the food given when its unconcious.