Short answer: Master NCERT first and add one practice book for subjects where you need more questions.
NCERT first
Finish NCERT exercises before looking for extra books.
Practice where needed
Add one practice book for maths and science if you want more questions.
Sample papers
Solve sample papers close to exams. Buy them fresh or check that the previous owner has not marked answers.
Frequently asked questions
Do I need many reference books?
No. NCERT and one practice book per tough subject is a good start.
Are second hand school books fine?
Yes if they are the current edition and in good condition.