Gallagher is a product of the Leeds academy, but has had spells with the Hull Kingston Rovers, the Keighley Cougars, the London Broncos, the Widnes (two spells), the Batley Bulldogs (two spells), the Rochdale Hornets and the Swinton Lions before joining the Leigh Centurions in time for the 2012 season.
Gallagher hails from the Leeds academy, but has had a series of transfers to the Hull Kingston Rovers, Keighley Cougars, London Broncos, Widnes (two spells), Batley Bulldogs (two periods), Rochdale Hornets and Swinton Lions before joining the Leigh Centurions in 2012.