A graduate of Gillingham's youth setup, Cundle signed a one-year professional contract with the club in the summer of 2015.[3] In the 2015–16 season, he had spells on loan at East Grinstead Town of the Isthmian League South Division, for whom he scored 11 goals in all competitions, 8 in the league; at Tilbury, for whom he scored twice in seven Isthmian League North Division matches in February 2016;[4] and at Margate,[5] for whom he scored once in five National League South matches in March. The goal came on his first appearance, in a 3–1 defeat against Maidenhead United.[6]
In May 2017, he accepted Gillingham's offer of a one-year contract extension.[10] On 7 November 2017 he scored his first goal for Gillingham in the Football League Trophy against Reading U21s.[11]