See your B.Sc wont be considered for GATE or even M.Tech. You need to complete M.Sc. Next, percentage doesn't matter to appear for GATE. You just need to have passed M.Sc. But for M.Tech admissions or PSU you will require at least 60% in your M.Sc. So study such that you have above 60% in your M.Sc since you will anyway be taking admissions in it.