So this is the setup I've decided to start working with in order to get started creating my own music.
Go here and download LMMS: https://lmms.io/ (originally called Linux Multimedia Studio)
It comes with about 20 instruments and native plugins, but you really need a few more for a really good digital audio workstation (DAW)
Luckily it has a single plugin called VeSTige that gives LMMS compatibility with VST plugins.
Here's a good place to start: https://www.musicianonamission.com/vst-instruments/
I started with Sound Magic Piano One as I treated myself to a decent midi keyboard and wanted a great Piano sound.
Spitfire LABS also gives you a dozen or so different instruments
Spitfire BBC Symphony Orchestra same again, only.. orchestral
These days though, as long as you have a good DAW, you're only limited by what VST plugins you can load into it.
Having a good midi instrument is great, though it's really a luxury if you're not great at playing it. LMMS allows you to use your regular PC keyboard as midi input.
You should probably get a copy of Audacity as well, for direct sound editing and recording.
But that's it so far. I will add to this article as I learn more.
Here's a guide to getting started: