GitLab CI build quarkus App with gradle


I’m currently trying to set up a CI build for a quarkus App which is build by using gradle. I’m totally new with GitLab and tried to find a solution by my own, but without success. I use the global runners and configured yml to use the gradle:jdk11 image and tried to install docker, but this did not work because of missing memory, so I currently don’t know if I try to do the wright thing, or if I should do it differently.
By using the quarkus plugin for gradle, the docker image is build together with the code (using: gradle build).
Any hints would be great.

Best regards