These links and tips are in no particular order, and I am not affiliated with any of the companies or developers mentioned here.
The plugins and instruments listed assume that your are using a DAW (digital audio workstation) that is PC or Mac based. If you do not (yet) have a DAW to work with, I recommend starting with Reaper - it is free/cheap (unlimited demo time) and professional.
This list is by no means exhaustive and still a work in progress 🙂
I hope it helps!
Kontakt is a widely used software sampler by Native Instruments. There is a free version of it (the Kontakt Player), but only very few 3rd party companies support the player with their free products.
Synth/Other/Mixed: