[znpy]

Been there, dropped 200+€ on rpis only to find out I then had to spend almost the same amount on microstld cards, power supplies, cables and all the other stuff.

Sold all those, recovered most of the money and bought a dismissed laptop from my employer of the time: 3rd gen quad-core i7, 16gb ram (later upgraded to 32), 480gb ssd + 750gb hdd for waaaay less (just the residual price)

Installed proxmox, created small VMS and played with k8s and a lot more stuff in a cheaper and more performant way (full gigabit ethernet when RPI has usb-shared ethernet, ssd-grade I/O performance, core i7 compute performance).

If you want to experiment the raspberry pi is the dumbest thing that you can buy.

Go for old hardware and virtualization, you'll also learn more (containers are here to stay, but VMs aren't going away either).

Power usage was also surely higher than a single RPI, but negligible anyway: laptop Intel processors with speedstep technology that lower down power absorption, and can go down to like 15-20 watts/hour.