Hello Swaroop Raj! 

It depends on which course you want to pursue in iit and also on which iit you want to choose.

Basically there are four main courses, machine design, thermal, production and industrial. Generally priority of most of the students are 1st design, 2nd thermal than any of the remaining two.At the spot admission in Bombay cutoff was

760-MMM,790-manufacturing,825-thermal,835-design

spot admission at guwahati

700-manufacturing,710-thermal,730-design

If your gate score is above 600 dont loose hope

Go for MS at IIT madras or IIT kanpur or RA at IIT bombay or try Direct Phd in IIT madras you can get a call for interview. 

I hope you get.