i assume that you are currently enrolled as an intern in IIT Madras. now coming to the GATE in my view for Gate exam one need ample time to prepare for as you have not mentioned your stream but still in order to achieve a good rank or say mark one need to be very efficiently prepared which can take up to a year to prepare for.

Since every student must invest some time of his academic life to attain internship. so you must complete your internship first. Internship from IIT Madras will make your cv very attractive and will play a very important role if you want to go abroad or want to pursue as a researcher in any reputed firm.

the internship is very vital for a resume frankly speaking one must adhere to the internship first complete it first and than go for GATE preparation.