Joining a coaching institute never guaranteees a good score, it all depends on your motivation and self belief and how much smart work and strategised planning you have made.

Taking up best coaching material and analysing mock exams is very critical for your success.

top books which can help you in lucid understanding and overcome doubts shared below.

Physics:-

Concepts of Physics Vol I and II by H.C. Verma

.New Pattern JEE Problems: Physics by DC Pandey.

Chmeistry:-

Organic Chemistry by O.P. Tandon

Numerical Chemistry by P.Bahadur

Mathematics:-

Maths XI & XII by R.D. Sharma

some best preparation tips you can vouch for shared below:-

https://engineering.careers360.com/articles/jee-advanced-preparation-tips-physics-chemistry-and-mathematics

To crack JEE exam it is not compulsory that you have to join a coaching institute there are many students who have cracked this exam by self study.

You should be highly motivated and determined to crack your exam and if you have taken a drop don't waste it, make it a count. You should try to take admission in one of the top colleges of engineering.

If you want to score good marks in JEE Main make sure your basics are clear. Make sure you read NCERT books throughly. So, that you can solve tricky questions easily.

You should be aware of the complete syllabus, exam pattern and important topics.You should complete your whole syllabus and focus on important topics more. You can solve as many as MCQs. For exam pattern and to know level of questions you can refer previous year papers.

Solve complete mock test series to work on your time management, to analyze your preparation level and to know your strength and weakness. So, you can work upon them.

Revision plays very important role in scoring good marks. You should revise your syllabus properly. You can make your important notes as well which will help you in revision.

All the best for your preparation!!