i am currently doing my b.tech in aerospace engineering , and i am planning to do my masters , what is the minimum percentile i need to get?

Thats a huge list and not all of it can be mentioned here. See if you get above 9 percentile then it is the best to start with. A minimum percentile as in eligibility generally starts with 60% if you take say IIT Bombay. GATE is one exam if you aim the IITs or NITs. Abroad - there is no collective list one can present. It depends upon the country and the university you wish to apply to. My suggestion here is that you first choose which country, see which are the best universities there and look up their eligibility. You can even write to them - they reply.