Scoring anywhere above 50 will be sufficient to get you an admission in branches other than CSE (because, there has been a considerable rise in demand for this branch and thus, the competition is tough). 

Even a candidate scoring around 19000 rank can get the desired branch easily.But, GITAM has students who have even scored negative marks in their GAT exam. So, needless to state, it doesn't matter how much you score, you will definitely get a admission in GITAM irrespective of how much you score in GAT.

I THINK YOU WILL NOT NEED TO GIVE ANY DONATION.

HOPE THIS HELPS!

ALL THE BEST!