What should be my strategy to score decent marks in Mathematics in 3 months?What are some low input high output topics?

Hey Apoorv

In 3 months you can develop yourself and can score very good score.
All you have to do is only practice and full devotion of your time and be concentrated toward your studies just forget about every other things and distractions.
First make the schedule and time table for study and all other works.
You should solve good books after you have done with all concepts and NCERT Book.
Mains and most important topics which are the base of mathematics are :
Calculus
Geometry
Algebra
Permutation and combination

So go with whole syllabus thoroughly with proper practice and concepts learning  and don't skip any of the topics and concepts .
Always talk to your teacher / guider and discuss about the problems and queries and doubts and don't think that ( skip that question I will do it later on).
First complete your previous concepts and work and than move forward.
Never loose hope even you get failure during these months because if you are preparing with proper concentration and dedication than it will definitely give results in the end.
So just calm and don't get frustrated .
And you should join a test series which give you time to time progress report and help you to analyse yourself.
So good luck

Hii Apoorv

since mathematics needs lots of practice and you are in 12'th as i see your profile,so i would recommend study all those imporantant part from where more question is asked. For instance calculas is the most important chap. of 12'th maths almost about 60% part come under calculas so you can study whole calculas easily in 3 months, well you can also target some small chapter as well like vector,matrices etc. as questions from these chapter are  very short and easy two understand as well doesn't need any high frustating concept to understand these chapter.

hope this will help you.

for queries you can further reply here.