Hey Akash

Since  Economics has been added only recently in IIT-JAM 2021 you need to know a few things about how to prepare for jam exam. If you want to go for online coaching institute then GATEIIT (Gate Indian Institute of Tutorials)  is the best as it has good experience in teaching economics. It has the experience hence your online classes will be well planned with results oriented method and online tests. Their study materials is also good.

You also have other sites like eduncle and unacademy so you can try them too but according to me getting enrolled in GATEIIT will be the best decision.