Hello Priyanka,

      I appreciate your interest towards UPSC examination and I'm here to help you and guide accordingly.

     UPSC is the examination which needs strategies to clear it. The major thing is not how much time you read and how much you read in the given time. Also, solving previous year papers is the key to success. Take mock tests whenever you are free and also reading newspapers will help you a lot. The NCERT books are the best books for UPSCa nd you'll also have many othet books such as India's Struggle for Independence by Bipan Chandra, Facets of Indian culture - spectrum, etc.., You should also improve your vocabulary and the last but not the least is the revision. Have proper time for revision and this decides your rank. 

Hope you find my answer helpful !!

All the best one for the exams!