Hello Kishan,

Your basics in Physics, Chemistry & Mathematics should be very clear upto 12th std. You should read the NCERT books for basics. Then HC Verma for Physics, RD Sharma for Mathematics, OP Tendon for Physical & Inorganic Chemistry, and Organic Chemistry of "Arihant Publication" for detail or extra knowledge. 
You should also try to solve the previous years question papers, this helps too much and you should also give the mock test to rectify yourself and build your confidence level.
For preparation of exam, the most important thing is your confidence after that you should know the whole syllabus and make your plan properly for learning new chapters, solving the numericals and revision. All three things should be the part of your preparation strategy in daily routine.
For more preparation tips, importants topics & books, you can go through the link given below
Https://engineering.careers360.com/articles/jee-main-2019
In this way, you can prepare well for the JEE Main and the JEE Advanced.
Thanks for query on this platform, you may visit again
All the best for your examination.

Dear Kishan Pandey,

Greetings.

Yes, NCERT books are the base for any kind of exam preparations. You should first try to solve examples, then you should try to solve exercise questions. Then, lastly you should solve sample papers of previous 5 years. Other than NCERT, you can also go for these books specially for maths preparation. 

Wish you all the best!