GATE Cutoff is determined by each IIT considering a lot of factors like the number of applicants for the particular M.Tech course, the total seats available category-wise for the course, previous year cutoff marks etc. It would be tough to tell you the exact but try to score more than 550-600 to get into IITs. You can also check the previous year cutoff with the given below link.

https://engineering.careers360.com/articles/gate-cutoff-for-iits

Good Luck!