Hii Saptarshi 

Most important will be the trignomentry because  paper setter try to combine questions from other chapters to this.next important one will be the calculus and geometry

In maths, a few important topics are:

1)Conic Sections.

2)Quadratic Equations- knowing the intervals in which roots lie will help you.

3)Differentiation - Keeping the formulas in mind will be very helpful to you ..

4)Vector Algebra.

5)Definate integrals and Area under the curve.

6)Limits ,Continuity and Differentiability.

7)Functions.

8)Complex Number.

Firstly learn each and every formula.this will help you the most..

All The Best !!