Now I am preparing for Jeemain. Now for I am going for the concepts of PERMUTATION AND COMBINATION, BINOMIAL THEOREM, PROBABILITY. In these three chapters which should be started first for better understanding of all the three concepts?
For JEE main all three of these are important, but for better understanding I would suggest you to start with Binomial Theorem-->Permutation and Combination--> Probability.
You can also check out the website for some last minute tips
https://engineering.careers360.com/articles/jee-main-preparation-tips
All the best for your exams!