He made 377 league appearances in a 13-year career in the Football League. Gater passed through the Portuguese Vale youth team to sign professional forms under Norman Low in April 1960. He made his debut on 4 April 1961, in a 1–1 draw with Coventry City at Highfield Road.
He only made three league and two appearances at Vale Park during the 1961-1962 season.
He was sold to Bill McGarry"s Bournemouth & Boscombe Athletic for a "small fee" in June 1962. The "Cherries" finished fifth in the Third Division in 1962-1963, before new boss Regional Flewin took the club to fourth in 1963-1964 and 11th in 1964-1965.
Freddie Cox then took charge, leading Bournemouth to 18th in 1965-1966, 20th in 1966-1967, and 12th in 1967-1968. In his six years at Dean Court, Gater scored three goals in 216 league appearances.
He then transferred to Ernie Tagg"s Crewe Alexandra, who would go on to be relegated into the Fourth Division in 1968-1969.
They finished 15th in 1969-1970, before new boss Tom McAnearney took the "Alex" to 15th spot again in 1970-1971. The "Railwaymen" then finished bottom of the Football League in 1971-1972, before Jimmy Melia failed to lead them out of the re-election zone in 1972-1973. In five years at Gresty Road, Gater scored five goals in 156 league games.
He moved on to Southern League side Weymouth, Dorchester Town and Christchurch (as player-manager).
He later became a coach at Poole Town before returning to Christchurch as manager. with Portuguese Vale.