Gamble helped the Eagles dominate in bench points 21-4.
Andre Smith scored 11 points and Steve Johnson added eight to help Winthrop (7-9, 1-3) snap a four-game losing streak.
Trailing at halftime 34-26, Presbyterian (3-15, 0-4) got within four points, 42-38, on a pair of Truss Williams free throws, but the Eagles answered with a 15-5 run to make it 57-43 with 3:10 left to play. Gamble started the run with a jumper, and Larry Brown capped it with a dunk.
Winthrop closed out the game converting 5 of 6 free throws down the stretch.
The Eagles made 17 free throws compared to Presbyterian’s eight.
Jordan Downing scored a career-high 26 points and grabbed eight rebounds to lead the Blue Hose, who have now lost four straight.