Firstly read all the ncert which is imp for upsc ncert clear your all basics while reading ncert you can also solve some prelims paper 1 questions of past years they after go for reference books.

NCERT Books for UPSC Preparation

NCERT books are considered to be the foundation for UPSC preparation. They provide a comprehensive understanding of various subjects and topics covered in the UPSC syllabus. As a first-year student, it is essential to have a strong foundation in the subjects that are part of the UPSC syllabus. Here are some NCERT books that you can refer to for UPSC preparation:

1. History:
- Class 6: Our Past - I
- Class 7: Our Past - II
- Class 8: Our Past - III
- Class 9: India and the Contemporary World - I
- Class 10: India and the Contemporary World - II
- Class 11: Themes in World History
- Class 12: Themes in Indian History - I, II, III

2. Geography:
- Class 6: The Earth Our Habitat
- Class 7: Our Environment
- Class 8: Resource and Development
- Class 9: Contemporary India - I
- Class 10: Contemporary India - II
- Class 11: Fundamentals of Physical Geography, India - Physical Environment
- Class 12: Fundamentals of Human Geography, India - People and Economy

3. Polity:
- Class 9: Democratic Politics - I
- Class 10: Democratic Politics - II
- Class 11: Political Theory
- Class 12: Contemporary World Politics, Politics in India since Independence

4. Economics:
- Class 9: Economics
- Class 10: Understanding Economic Development
- Class 11: Indian Economic Development
- Class 12: Introductory Macroeconomics, Introductory Microeconomics

5. Science:
- Class 6: Science
- Class 7: Science
- Class 8: Science
- Class 9: Science
- Class 10: Science

6. Environment:
- Class 7: Our Environment
- Class 11: Fundamentals of Physical Geography
- Class 12: Fundamentals of Human Geography

These NCERT books will help you build a strong foundation in the various subjects required for the UPSC examination. Additionally, reading these books will also enhance your conceptual understanding, which is crucial for answering questions in the UPSC exam. Along with NCERT books, it is also important to refer to other standard reference books and current affairs magazines to supplement your preparation.