hello atharva......

the important topics in jee of physics are

newtons laws  of motion

bernoullis theorem

equation of continuity

elasticity

electro statistics

current electricity

optics

important topics in mathematics

statics and probability

applications of integrals

vectors 3D

definite integrals

trigonometric ratios

determinants and matrices

important topics in chemistry

nomenclature,types of reactions,basicity,acidity these are from organic chemistry

method of preparation,chemical reactions,uses etc these are from inorganic chemistry

fazans rule and its application,molecular orbital theory,transition elements and coordination chemistry,hydrogen and s&p blocks,atomic structure,equilibrium,solutions,surface chemistry

i hope this information is helpful

all the best.

For JEE main every topic is important because they ask questions from almost all the Topics every year but few topics are there which they never skip asking questions

For Physics: Give importance to Electrostatics, Optics, Mechanics, and please don't ignore experiments which are mentioned in Mains like vernier caliper they ask questions every year, they may ask questions on significant figures.

Chemistry: Focus on organic reactions they will ask direct questions on them, Properties of Inorganic compounds, Chemical bonding is also VERY important. Just focus on NCERT you will score well.

Mathematics: Calculus and Coordinate Geometry is most important there will be many questions from this two topics.