Depending on where you find the giga there are 2 good things to do. The most wise thing to do would be to get a flying mount and lure it away from your base. Do you need to wreck a tribe without being found out? If yes the read on. Lure the giga into your enemy's base, the giga will wreck all their dinosaurs as wild gigas are not nerfed therefore even if they had a giga the giga you lured would survive. -NOTICE- do this if you do not enough to power to tame one, they are an extremely good bullet sponge.
On ragnorok there is a spawn place in the grass lands by the light house near the wyvern trench also I used about 40 shock darts and 300 bio toxin on tameing one put be worned a level one wild giga has 80000 health and 100 present melle damage. A tamed level one giga will have 20000 and 25 melee damage . Thumbs up if this has been helpfull to you