HI RAJESH,

Marks of 90 and rank of 75000 as acquired by you in the jee main 2018 is not sufficient for you to get any stream in any of the NITs across INDIA.

So,I would suggest you to try for start applying in the private engineering colleges like VIT(Vellore INSTITUTE OF TECHNOLOGY),KIIT,SRM etc.

Also try to score good in your JEE ADvanced so that you can get through the ADVANCED and get a decent IIT.

BEST OF LUCK BUDDY!!

Sorry to say but you didn't scored enough to get seat in NIT as the cut offs for NITs for any branch is very high as compared to other colleges If we have a look on previous year cut off in general you need to score below 50k to get into NITs and below 20k to get into top NITs with you desired branch and as long as seat in other collgese linked with jee mains are concerned you might get admission but you wouldn't be able to get top branches like CSE and ECE. you can see what colleges you might get with this rank with the help of our jee main college predictor you just need to enter your rank your category,your home state and your desired branches and you're good to go and you can even have a look on previous year cut offs of NITs and other colleges. I am providing you the link for all. 

https://engineering.careers360.com/jee-main-college-predictor

https://engineering.careers360.com/articles/jee-main-cutoff-for-top-nits

https://engineering.careers360.com/articles/jee-main-cutoff

i suggest you to look for some backup options as there are many engineering enterence exams nowdays if you have given them then all right and if not then you should go for some good private colleges like Gagotias, manipal,SRM,MMM and so on and side by side you can go for the counceliing of jee mains too and see what you get.

Good Luck!!