Hello Aspirant,

The plan that you are proposing is not enough to get you to an IIT. It might, if you are very very good in Mathematics, help you clear mains but yet you won't end up getting a good college because of the competition. You will merely be able to clear the cutoff of your category which is not enough to get you a proper seat in NIT with a proper branch, of your choice. And next comes advance. Which is a harder but to crack. 

You really need to have a good-hard control over the three subjects to make through both mains and advance and ensure a quality seat in a quality branch in a quality IIT. 

All the best .