Gavin McMillan began playing football at Camdean, then went to East End Swifts before joining Dunfermline at U10 level. He rates his biggest influencer as his dad but credits Stevie Paterson as one of his best coaches. Gavin attended Inverkeithing High School and Inveralmond High School and to end the season playing in the U20s exceeded all his expectations for 2012-13.
Although admitting to be surprised, he was pleased to be offered a contract at Dunfermline until the end of May 2015. Left when contract ran out and joined Stenhousemuir for season 2015-2016.