I would agree with @kevdog that Docker is one of the best places to start.
You can start learning Docker without a lot of hardware. I am actually running it by way of a VM on my Unraid server since I didn’t want to buy a new host just for Docker. The VM is allocated with 2 vCPUs, 8GB of RAM, and a 50GiB vDisk. I’m running Ubuntu Server 20.04 LTS. I use Docker compose for my Docker containers.
Definitely check out Jay’s videos on YouTube. Jay is a great resource for learning about Docker and Linux in general.
One thing to explore is Kubernetes/K8s. I don’t know a lot about it, but I think it’s prudent to mention before I “sell” you on Docker. Many people say that K8s is more modern than Docker specifically if you’re looking to build clusters, whereas Docker swarm is not as actively developed these days. I don’t use clusters (yet) so this isn’t something that I know a lot about, just figured I’d mention since K8s and Docker are very similar and I think anyone who is interested in one may want to check out the other to see which is best for their needs.
That being said, Docker is awesome and I think the learning curve is very manageable for new users.