Ha, I also got most of my initial experience the same way :) I use k8s at work now, am somewhat frustrated with it and would like to run a k8s cluster at home, but I have a hard time justifying it. I'm not sure if a pi k8s cluster would make sense for me either, although I do have enough pis laying around for a small-ish one. I've considered ordering a couple (more) r210 ii's and making a cluster, but don't know what the stack would be exactly.The beefiest machine in my home currently is an unraid server, and I run a small number of services in a docker-compose stack on a vps.
Do you find that there are functions that are unique to k8s for a selfhoster that demand a system with that kind of overhead?
Setting stuff up in order to have fun with it and learn is always worth it. It's "always" worth it to use overkill on a personal project.
Of course you don't need that k8s cluster and of course you shouldn't really use pis. But it'll be fun. You could also just use 10 vms running on your computer and each vm is one node in the k8s cluster if you don't want to buy hardware. Then you see what happens when "hardware failure" occurs. I.e. you kill a vm without shutting it down properly. Or yank the power on one of the pis.
The point is, once you need it for a real project now you know how it works and when to actually use it and when not to. Heck all the stuff I set up on my single old 200MHz system, no vms nothing taught me basically everything I needed to become an actual sys/network admin later.
Do you find that there are functions that are unique to k8s for a selfhoster that demand a system with that kind of overhead?