I would like to share my experience from the point of view of student who had coaching. I joined Made Easy while I was in my final year. Some teachers were quite awesome but others were just fine. The most important advantage of joining coaching classes is that they make you regular in your studies other than that you have to do all the things by yourself. I started following Gateoverflow when there were 8-9 months left for the exam.
According to me, to get a good rank in GATE you'll need the following 3 resources:
1) http://gateoverflow.in/ : To get the clear and accurate explanations of all the previous year questions and other NON-GATE questions. Gateoverflow book contains all the questions compiled into pdf format and I highly recommend you to solve it THOROUGHLY!!!
2) http://www.gatecse.in/ : To guide you about how to do your preparation, books to study, lectures to watch, etc.
3) https://www.facebook.com/groups/gateoverflow/: This group is going to play one the major roles in your pre-GATE as well as post-GATE preparation. Experts like Arjun Suresh, Praveen Saini, etc as well as other group members are going to help in your technical as well non-technical queries.
You shouldn't get affected by the questions that you are able to solve easily but the ones that you're not able to answer should bother you. Solve to learn new concepts and not to increase your count. According to me, the quality of your preparation is going to give you a good rank rather than the quantity. If you find any difficulty during your preparation you can always contact me (firstname.lastname@example.org)