WBJEE is comparitively easier than JEE main, therefore if you are able to solve JEE main Physics and Mathematics questions, then no need of worrying.
Both of these subject are conceptual, and the more you practise, the more shortcuts you discover. Try solving solved question first, and build your concept.
Whereas if you want to improove, I suggest you to go through the standard books such as H.C Verma, I.E. Irodov, D.C Pandey, and NCERT. For WBJEE, NCERT and H.C. Verma would be enough. Apart from this you may also consider the past year papers.
For mathematics, the more you practise, the less it is. Therefore, I would suggest you to go through as many books as time permits, for Maths. Consider, RD Sharma, NCERT, your school Text Book, Mathematics by R.S. Aggarwal, and of course previous year papers of WBJEE.
In case you fall short of material, go for some good coaching institute material, or solve JEE problems.
Hope this Helps
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