

A degree will help you get in the door and it will teach you the theory behind the practice, which is helpful for the problem solving parts.
Other than that, read good code and write lots of code, even if it’s crap, as long as you’re learning from your mistakes. Experiment and venture outside your comfort zone. Don’t focus too much on leet coding.
Contribute to open source if you can. I’m always happy to see a candidate with a solid GitHub profile, where I can see actual code that they wrote. It will also teach you to collaborate with others.
But mostly: stay curious, and don’t stop learning.
Are you telling me Beowulf clusters are back?
Jokes aside, it depends what you want to do. You can’t really build one powerful gaming PC out of multiple, but your can run parallel workloads in a number of different ways. What exactly, comes down to what you’re doing. A kubernetes cluster is different from a Blender render farm, for example.
As others mentioned you can just remote into the servers with ssh, vnc, rdp, etc. if you want physical displays on them, you can look for a cheap KVM which lets you control multiple PCs with one keyboard, monitor, and mouse.