For writing GATE there is no minimum percentage criteria. But for admission into top institutions like IITs and NITs, in addition to good GATE score they ask the percentage of usually 60% or 65 in b.tech but there may be relaxation for the reserved categories.
The percentage criteria varies for the other institutions. As you still having one year of study work hard and try building up the percentage and parallely prepare for the competitive exams.
All the best