Hi Dear, as you saw last year jee-main cutoff was 32 for ST students and this year expected cutoff will be >=30.jee-main ranking depends on the 12th board's marks.if your 12th percentage good and jee-main marks are 63 then you will get most of the NITs, IIITs, and GFTIs.

for college NIT/IIIT and more check college predictor:
https://engineering.careers360.com/jee-main-college-predictor

for more information check it out given link that will help you to check cutoff ranking for NITs, IIITs and GFTIs :
https://engineering.careers360.com/articles/jee-main-cutoff