Exam

To take admission in government colleges, like IITs, you have to score above 97 percentile. For NITs, you have to score 80% to 97% marks. For government colleges other than NIT or IIT, you have to score above 75 percentile marks.

If you have less CGPA in B.Tech, then you should score good marks in GATE exam, otherwise you will not be able to get admission in top colleges.

GATE is not for undergraduate courses. It is for PG. You have got only 48% marks. My sincere advise is to leave obsession with engineering and look for something different. Go with your passion. Commerce, arts, fine arts, there are different courses that you can choose.

You need to score a decent percentile (Above 98 percentile), as most students appearing in GATE are from CS stream.

Yes of course, GATE (Graduate Aptitude Test in Engineering) is for the admissions into IITs and other reputed colleges for M.Tech or ME courses.

All IITs use Graduate Aptitude Test in Engineering GATE score for admissions to various post-graduate education programs (e. g. Master of Engineering, Master of Technology, Doctor of Philosophy). There is no direct admission in higher studies at IITs except for sponsored candidates.

Every IIT has it's own cutoff for admission in different branches.
So, I suggest you to score more as much as you can.
Do hard work and try to solve the paper correctly and less mistakes.
Just check the cut- off for the IIT
You can see the cut-off that is so high
Just concentrate on your studies and focus.

You must specify which course you want to pursue and the stream in which you are interested.