As for Jee mains, Organic chemistry has more weightage than inorganic and physical chemistry. But to score 100-120,you need to concentrate on all the three parts of chemistry. If your aim is scoring 100-120 then i would like to suggest a plan for all the subjects

1)Completing ncert textbook entire is more than enough to get good score.

2)practice all the previous question papers and model papers

3)write down all the formulae and equations in the textbooks

As for chemistry concentrate more on organic then physical and then inorganic.