Dear aspirant,

If you are thinking of just clearing the cut off in obc category then it's of no use as the cut offs are high in the nits. You should aim for scoring as much high as possible and to score that much percentile I don't think you should be selective about the chapters as you need to have grip on your subjects.

But if you want to prepare first easy ones then start with chemistry -organic (biomolecules , polymers, environmental chemistry) , Maths- mathematical reasoning, statistics, probability ,Physics- Semiconductor , communication systems.

https://engineering.careers360.com/jee-main-college-predictor?icn=QnA&ici=qna_answer