You only need to read these 6 NCERTs for UPSC prelims:-
1- 4 geography NCERT of classes 11 and 12th
2- Ancient history NCERT- can read any NCERT(old/ new)
3- Medieval History NCERT - can read any NCERT(old/ new)
4- Fine arts NCERT for class 11, which is for art and culture.

Typo:-7 NCERTs

You have to read other basic books too like laxmikant, spectrum etc but for ncerts these are enough