Hi,

MAINS:

In physics give most importance to Current Electricity, Electro statics, Optics, Modern Physics, Heat and Thermodynamics.

Under Mathematics, Coordinate Geometry, Limits and continuity and differentiation, Integral Calculus have high weightage. 3D Geometry, Quadratic equations and Complex Numbers, Statistics and Probability also have good weightage.

In Chemistry, Transition elements and coordination chemistry, thermodynamics, periodic table and its groups, surface chemistry and solid state, chemical and ionic equilibrium have high weightage.

(https://engineering.careers360.com/articles/jee-main-syllabus-weightage) 

ADVANCED: https://engineering.careers360.com/articles/jee-advanced-syllabus

• By solving last year papers you can self realise that.
• I would suggest that do it by your self(do analysis of few past year papers)  so by doing that find some topics by yourself
• You will understand types of question iit jee ask.