Gareth began his representative rugby career playing for Durham County's under-16 team while he was with the Chester-le-Street club. He went on to play for the county at under-17 and under-18 levels as well as the North of England at under-17 and under-21. He was in the Chester-le-Street team who were Durham County under-16 champions in 1994 and under-17 runners-up the following year.
Bury-born Gareth joined Newcastle from West Hartlepool in 2000. Gareth has a residential qualification for Scotland.