If you are looking for a way to gain knowledge in a lot of different ways (Kubernetes including ingress, services, and COS as a way to holding information, plus Terraform and more) then I recommend this article.
It has a link to a repo you can use that had 2 issues at the time, so I forked a copy and in the meantime to fix the issues. You can get it here.
What’s nice about this is it comes with some shell scripts that use terraform to build and configure the cluster. It’s a good way to learn many things at the same time. Recommended.