Hiiii dear!!!! Below I have mentioned some of the best insInstites for UPSc preparation: 

• Vajiram and Ravi IAS coaching.
• Plutus IAS coaching.
• Analogue IAS academy.
• Ramanasri Institute for upsc.
• Als IAS coaching.
• Drishti IAS coaching.
• Khan study circle.
• Sri Rams IAS coaching.

greetings,

when it comes to UPSC coaching, rau ias academy and chanakaya academy are household names.

pls refer to the link below for more infomormation:

https://competition.careers360.com/download/ebooks/upsc-civil-services-exam-guide

https://www.chanakyaiasacademy.com/

https://www.rauias.com/

hope this helps.

good luck