Hello Avinash,

There are books and resources which will help you gain knowledge and Prepare for the competitive exam:- 

• History, GCERT std 11 and 12
• Geography, GCERT std 11 and 12, Oxford Student atlas
• Constitution, Liberty GPSC Class I and II Bhartiya Arthvyavastha and Rajyavyavastha latest edition 2018
• Maths and Reasoning, liberty GPSC Class I and II Samanya Budhik Kshamta(Maths and Reasoning)
• Central and State Government Schemes by Vision IAS
• Liberty GPSC Subjectwise Questions. Latest edition 2019
• Liberty GPSC Class I and II Prelims' Current Affairs, edition 2018.
• Newspaper:- The Hindu, Times of India, Dainik Bhaskar, Navgujarat Samay
• Magazines:- Pratiyogita Darpan

Hope this helps.