Hello Taru,
There is no online coaching for GATE exam, you can definitely try Byjus, Unacademy but I would say don't go for that. Only test series is available online which is a must. You will be able to ask doubts frequently to your tutors.
For offline coaching for GATE exam, some of the best coaching institute are:
Made Easy and ACE academy
Answer Key | Application | Eligibility | Exam Pattern | Admit Card | Preparation Tips | Books | Accepting Colleges
Regular exam updates, QnA, Predictors, College Applications & E-books now on your Mobile