This is how I got started. HP Elite desk Mini. If you want room for full size HDDs then get the SFF version.

Try to replicate software/apps you use everyday. Not to improve them, but to figure out how they work. In addition to learning how they work, you’ll learn the problems the original devs had to solve, and one way to solve them.

Vaultwarden is pretty game changing. No more reusing passwords and they aren’t in the cloud.