For any competition all topics are important but you have to choose which is your strong part(PCM). Most of the students only focused on 12th class topic .
And in PCM chemistry is easy from my point of view(priority order : 1 . Organic 2.Inorganic 3.physical) and do practice on maths and try to learn the concepts of physics and solve as much problem you can solve before the exam.This will help you more.