If your main goal is a monero node/mining, start with AMD 3000 series processors, 3700x is a good place to start, and build a used system. If it’s just a node, any SoC will work with enough storage. A few months of a VPS could cost the same as buying your own hardware, that and you own the hardware and data instead of some corporation.

Everything runs in a docker container, so you will probably want to wrap your head around that first thing. Most people start with portainer or dockge for easy docker management and learning with a gui, although learning everything through the command line has its merits as well.

I would get a raspberry pi or an old NUC and just dive right into figuring out how to run the monero node. I believe the monero project maintains docker images. The monero communities are super helpful and nice, and so are the self hosted communities, if you hit a snag or don’t understand something.