System
It's easy to lose settings from one computer to another, so it's important to take notes and document the way you like things configured.
Hardware
Computers need hardware to run on. These are the systems that power the devices and applications we've come to rely on.
If you're just getting familiar with this space, the [Raspberry Pi - /pi/) ecosystem is a great place to start. Heavy overlap with this space.
Operating Systems
Set up a computer with a fresh operating system.
If you don't already have a preferred operating system, consider one that is open source. Open source software is a wonderful thing, but don't just take my word for it.
Linux is the most common on desktop machines in the open source world. There are many flavors:
In the mobile phone space, Android is a good open source solution.
Applications
Administration
Tmux
SSH
Terminal
Bash
Shell
Bash Colors example available in linux/bash-colors.sh
Checksums
Firewall
Network
Nginx
Remote Desktop
Startup Services
Search
From the command line
find * -iname "*search-term*"
to find files that match a pattern.