As a starting point. Are there any hardware recommendations for a toy home server?

Whatever you already have. Old desktop, even old laptop (those come with a built-in battery backup!). Failing what, Raspberry Pis are pretty popular and cheap and low power consumption, which makes it great if you’re not sure how much you want to spend.

Otherwise, ideally enough to run everything you need based on rough napkin math. Literally the only requirement is that the stuff you intend to run fits on it. For reference, my primary server which hosts my Lemmy instance (and emails and NextCloud and IRC and Matrix and Minecraft) is an old Xeon processor close to a third gen Intel i7 with 32GB of DDR3 memory, there’s 5 virtual machines on it (one of which is the Lemmy one), and it feels perfectly sufficient for my needs. I could make it work with half of that no problem. My home lab machine is my wife’s old Dell OptiPlex.

Speaking of virtual machines, you can test the waters on your regular PC by just loading whatever OS you choose in a virtual machine (libvirt if you’re on Linux, VirtualBox or VMware otherwise). Then play with it. When it works makes a snapshot. Continue playing with it, break it, revert to the last good snapshot. A real home server will basically be the same but as a real machine that’s on 24/7. It’s also useful to test things out as a practice run before putting them on your real server machine. It’s also give you a rough idea how much resources it uses, and you can always grow your VM until it fits and then know how much you need for the real thing.

Don’t worry too much about getting it right (except the backups, get those right, verify and test those regularly). You will get it wrong and eventually tear it down and rebuild it better what what you learn (or want to learn). Once you gain more experience it’ll start looking more and more like a real server setup, out of your own desire and needs.