The method I've been using successfully:

1. Git commit triggers CircleCI build and test phase

2. CircleCI deploy phase uploads the image to GKE

3. Google Container Engine stages the deployment for release

Can you link to an article on 3) ? We have been releasing by invoking kubectl from Circle, I wasn't aware that GKE can release itself.

Jenkins 2.x for building the images (we just execute docker build and push in a Jenkinsfile), then we use Kontena for orchestration (e.g. the Kontena agent pulls the image from the docker registry). For local development we use docker-compose.

Jenkins and the Jenkins slaves also run on docker, and are managed by Kontena. In fact, the whole platform/pipeline runs completely on Docker. We use Ansible to install Kontena/docker on new servers.