Hello,

When it comes to State PSCs, you can start with NCERTs book, it's written in simple and lucid manner, and it'll provide you strong foundation, always keep resources minimal, read one book many a times instead of many a book one time, revision is the key here and read any newspaper such as The Hindu or The Indian Express with emphasis on Editorials section, this will help you a lot

For Prelims, you can refer the following books:

History ;

• NCERT Class XI and XII
• India's Struggle for Independence by Bipin Chandra
• For Indian Culture, refer art and culture by Nitin Singhania

Geography ;

• NCERT Class VI to XII
• GC Leong's Physical Geography
• World Atlas

Economics ;

• NCERT Class XI
• Indian Economy by Ramesh Singh

International Relations & Polity ;

• NCERT XII Political Science with current affairs
• Indian Polity by Laxmikanth

Mental Ability/

• Verbal and Non-Verbal Reasoning by RS Agarwal
• M Tyra's Quicker Maths

Coming to Mains Exam, you can refer the following books for  General Studies Paper;

• GS I - For History , Class XI NCERT book with India's struggle for Independence by Bipin Chandra,India after Independence by Bipan Chandra,History of Medieval India by Satish Chandra
• For Geography refer World Geography and Geography of India by Majid Hussain, GC Leong's Physical and Human Geography with NCERT Class XI book.
• For  Polity and International Relations , refer Indian Polity by Laxmikanth,India's Foreign Policy by Rajiv Sikri
• For Economics refer Indian Economy by Ramesh Singh, read ARC report along with Economic Survey and Fiscal Budget.