Kostons progressed through MVV's youth academy, joining their setup as a thirteen-year-old from boyhood club Lanaken VV.[3][4] In the 2016–17 Eerste Divisie season, he was included in the matchday squad of the first team on several occasions, but did not yet make his debut.[3] He made his debut on 19 September 2017 in a 3–2 loss to AZ in the KNVB Cup, replacing Christophe Janssens in the 90th minute.[5][6] Kostons made his league debut on 6 October 2017 in a 3–2 loss against Almere City, coming off the bench in the 88th minute for Shermaine Martina.[7][8] On 24 November 2017, he scored his first professional goal in a 3–1 victory against Helmond Sport.[9]
Dalkurd
On 27 July 2021, Kostons joined Swedish third-tier Ettan club Dalkurd.[10] He made his debut for Dalkurd on 15 August 2021, also scoring his first goal for the club, in a 1–1 draw against Umeå FC.[11]
He was part of Dalkurd's promotion to the second highest level in Sweden, Superettan, scoring 11 goals in 16 appearances.[1][12]
Return to MVV
On 4 July 2022, Kostons returned to his former club MVV on a two-year contract.[13][14] He made his return debut for MVV on the first matchday of the 2022–23 season, starting at forward alongside Orhan Džepar in a 3–1 loss to Jong AZ.[15] The following week he scored his first goal for the club upon returning, opening the score in a 3–1 home win over NAC Breda.[16]