from where I can get useful notes and materials for jee mains ??

First read the concepts well from the ncert materials. Be perfect in the concepts. Then go for cengage or arihant books ( a few of them are exclusively for mains). Solve them. Check the models of the question. Ask your lecturer to give a few more models. And try to solve those paragraph based questions in FIITJEE material. Concepts concepts concepts. Concepts first. Problems next. Try to figure out some new models of your own so that it may improve your thinking standards.

Refer a few materials like arihant and cengage. Practice previous papers. And that's enough to crack mains.

You can follow below recommended books for your preparation

Physics

HC Verma – Concepts of Physics (Part I)
HC Verma – Concepts of Physics (Part II)
IIT JEE Physics – DC Pandey
Problems in General Physics – I.E. Irodov
Physics for IIT-JEE – Resnick, Halliday, Walker.
Problems in Physics – S.S. Krotov

Chemistry

Organic Chemistry – Morrison Boyd
Organic Chemistry – O.P Tandon.
Modern Approach to Chemical Calculations – R.C. Mukherjee
Numerical Chemistry – P. Bahadur
Concise Inorganic Chemistry – J.D. Lee

Mathematics

IIT Mathematics – M.L. Khanna
Differential Calculus – A Das Gupta
Class XI & XII Mathematics – R.D. Sharma.
Trigonometry, Geometry Books – S.L. Loney.
Problems in Calculus of One Variable – I.A. Maron
Higher Algebra- Hall and Knight

All the Best!!

Go through with NCERT books first then You can prefer Akash, Ressonance & Allen study material for your preparation. You can prefer other books as well given below.

Physics - HC Verma(concept) and DC Pandey(problems).

Chemistry - LG Wade organic chemistry, JD Lee Inorganic , OP Tandon Physical Chemistry and NCERT

Mathematics - Arihant series and RD Sharma

Good Luck!