As there are many available and you should research at your level as well and join the one as per your interest, convenience and make sure that the teaching strategies are helping you to make all your concepts strong and their preparation books are easy to understand but generally below mentioned institutes are decent for the same -

Gate Forum

Vani Institute

Ace Academy

IES Academy

The Gate Academy

 Also, if you talk about the fee structure then it depends on course, duration and institute wise so I would suggest you to shortlist the one and visit the center to get all related information.

Good Luck!!!