Breed a giga, put a good saddle on it, kill everything, titans wild gigas etc etc. Breed one is like breeding five, so always breed more than one. Imprinting them at best will give them a real better hp and dmg, all the other stats are ininfluent. Always level only attack as the other stats will grow nothing when levelled.
WHEN TAMED! On a pvp server mostly make sure 100% of the time he/she is in a separate cage completely away from all other Dino's!! This is because after a certain amount of dmg done to the giga he will begin to "rage" he will turn on you even after all the happy memories you've had. Also even attacking all his Dino friends! :( so be sure to lock up this beast of a Dino!