Dear Arushi,

In order to score good marks in NEET it is very important that your concepts should be clear and you build strong fundamentals.

NCERT is important book  for your preparation. Exercises which are given at the end of completing each chapter is extremely important as you can get direct question from there. 

With the help of crash course you can complete your course in short span of time. If you know how to prepare for your exam in last days you don't need a crash course but if you are clueless you can go for it. 

Crash course will help you in guidance and motivation. 

Make sure you solve previous year questions and complete mock test series for your practice.

Good Luck!!