The Republic of Ireland Under-21 international is expected to provide back-up to regular number one Clayton Ince next season but is hoping to make the breakthrough at first-team level.
Gilmartin spent time on loan at non-league Hednesford Town during the recently completed season.
"I want to continue improving and hopefully grab my first-team chance with both hands if and when it comes along," he said.
"There is sure to be a chance for me somewhere along the line and it is up to me to take it and show the gaffer what I can do."