yes, you can.I feel 6 months are enough to prepare for GATE exam if you are willing to dedicate that 6 months fully and concentrate only on GATE. And if you have strong concepts than all you need to do is practice a lot of questions only that will make you crack GATE exam.

you can join coaching and test series to bound yourself to GATE exam. If you join GATE joining it will help as they will guide you what to do and want not to do the limited period of time remaining for GATE exam.