hi,

see there is no age restriction for appearing in Gate exam, also education gap does not matter, there is no age restriction for doing m.tech or higher study. But gate exam is not easy and it difference then college exam. gate paper is based on numerical question with conceptual part. so you have to prepare for it while working. also do think is gate is the exam you wants to appear or you want to apply for others job relevant to your areas. however Gate score is beneficial for psu hiring. top psu in India hires based on gate score.

you have to again start preparing for gate exam, first start revise the basics of theory. it is advisable to take coaching or follow youtube lectures on your relevant stream.

hope you understand.