I'm sure there's been a post like this already, but I am currently trying to find ways to practice stuff at home while not breaking the bank. I am using cisco Packet tracer for testing and playing around and I've been thinking about buy a Raspberry Pi or two. I'm just curious if there is anything in addition I could do until I have more money to but some nicer stuff.
For networking a decent PC with proxmox can be the whole lab. If you can run a server and 2 client machines, that's enough for most network testing.
If you want to go full hardware a decent PC and two low end HP workstations running win 10 will do.
You can lab it all out in software or build various networks.
I'd look for used SFF dell, hp or Lenovo machines. Or just get a server that can run four VMs.