In Jee,It include physics, chemistry and maths and in NEET , it include physics , chemistry and biology.
In jee you must need to concentrate the subjects are chemistry and physics.
And in NEET you must need to concentrate chemistry and biology.
In my opinion you you can give more importance to the subject chemistry then biology then physics and then mathematics.
And your result is depends on the time at which you workout the problems.
You must do previous year questions in every weekend and also do daily practice problems.
From this you will get an idea about the exam , which help you more to prepare the exam.
At the time of JEE exam , you can leave the subject biology.
And at the time of NEET exam you can leave mathematics.
Wish you all the best for the all exam's.