You should focus on the core topics from the Class 11 and 12 syllabus of Physics, Chemistry, and Mathematics as prescribed by the NTA. Some of important topics

Mathematics:

1. Coordinate Geometry
2. Calculus (Limits, Derivatives, Integrals)
3. Algebra (Quadratic Equations, Complex Numbers)
4. Matrices and Determinants
5. Probability and Statistics

Physics:

1. Laws of Motion
2. Current Electricity
3. Thermodynamics
4. Optics
5. Modern Physics

Chemistry:

1. Chemical Bonding
2. Organic Chemistry – Reaction Mechanism
3. Coordination Compounds
4. Equilibrium
5. Thermodynamics

Also practice previous year's papers and attempt mock tests regularly. NCERT books are very important, especially for Chemistry. For polytechnic students, strengthening your Class 11–12 concepts is key to cracking JEE Main.