The only way to prepare for Mathematics is by practising Mathematics. You need to focus on Algebra, Calculus and Trigonometry. Chapters like Vectors and 3D needs special focus. Complex number is a chapter from which atleast 2-3 questions are asked. So you need to master complex numbers, Vectors, 3D and Definite Integral. You should learn all aspects and results of Algebraic Calculations of properties of conics. Under Calculus, Functions, Application of derivatives need to be learnt too. Trigonometry is a scoring topic and so you need to grasp all the important formulae. Mathematical Reasoning/Determinants/Statistics/Mathematical Induction fetch you quick marks and so you need to cover them as well. Refer to as many as Sample papers as you can. We also have JEE Knockout package for students: https://learn.careers360.com/engineering/jee-main/.