1. How to start creating and/or publishing
The only free software with intuitive UI I know is Studio One Prime, LMMS and CakeWalk, but you can also evaluate a fully functional version of Reaper for two months, and the paid licence is cheap. Getting good studio headphones is cheaper than getting good studio monitors (speakers) plus room treatment etc. Keep in mind that to record any external sound, you'll need a good audio interface (soundcard) - even more than a very good microphone if applicable. I'd also highly suggest getting (at least) a 4-5 octave MIDI keyboard at some point. There are some self-contained hardware options with different workflows, like the OP-1, but you might instead want to look into specific purpose gear, like the Korg nanoKEY Studio as a MIDI controller for workflow variance, or the DS Mopho/Tetra as a versatile synth/sound module. Just make sure to do your research before buying (YouTube is a great source to see how a piece of hardware works!).
After getting a DAW and/or hardware, I'd suggest getting some plug-ins and samples (I listed my favorite sources below) - you don't really want to rely solely on the built-in stuff. Make sure you know the difference between generators (samplers/libraries and synthesizers) and effects. Learning the basics of plug-in/gear parameters like ADSR might save you a lot of time you'd otherwise spend on trial and error. Even if you don't plan to use synthesis or pure software that much, all of these seem to come in handy at one point or another.
Learning to mix seems a bit more trial and error-based than theoretical, but there's some suggested reading below too. Just don't fall into the "I'll fix everything with a compressor later" trap, and don't be afraid to spend time actually adjusting the levels and whatnot. Contrary to the general advice (regarding not comparing ourselves to others), I think it's good to refer to professionally mixed tracks as a kind of a guideline. This can be useful if you're tired and having trouble figuring out if there's anything missing in your song too. Just remember to treat it as a rough guideline and not a specific goal, and that there could be huge discrepancies between you and them regarding budget and the number of personnel.
What makes particular works (and their separate sections) stand out might be style-dependent, but you need to grasp the abstract of scale degrees and harmonic functions of chords, and be able to conceptualize them instead of relying on the note names themselves anyway. An advice such as "use more extended, borrowed and/or secondary dominant chords for harmonic interest" will mean nothing to you if you're not sure what a chord is. Many people do indeed "only go by ear", but the harsh truth is that it very often really is just reinventing the wheel (yes, even if you're trying to do something original or within a very niche subgenre). Don't be afraid to learn music theory - you really need to learn the rules before you break them creatively. Watch Adam Neely's "Why you should learn music theory (Prescriptivism vs Descriptivism)" video for a great explaination of this! All that aside, I still think that practice is more or less equally important - this can include transcribing and analyzing others' works. You probably need to read about, for example, voice leading to understand what's going on, but only practice (preferably with a keyboard) will make you remember how close are certain chords to each other in particular inversions, etc.
Unless you only aim for academia/historical accuracy (or the most approachable and not at all eccentric stuff like stock music), try to learn more than just the common practice period parts. If you feel like something sounds unusual but you still like it, the only question left to ask is, "do I WANT this to end up sounding unusual?". Even if you don't particularly plan to compose eerie 12-tone row-based works or jazz or whatever, it's irreplaceable to know a lot of these guidelines and tricks to avoid getting uninspired (tip: try discovering new genres too). Again, remember that music theory is not prescriptive! Would (doing this and that) be "forbidden" in the Baroque era? Probably, but it doesn't mean you shouldn't do it if you like how it sounds. Otherwise, we would never have stuff like jazz or most of today's electronic music! Vampires are also "historically inaccurate" and yet millions of people love them, right? (I strongly recommend watching "The Musical Fusion of the Castlevania Series" by 8-bit Music Theory to see some really cool examples of this)
The amount of knowledge and practice you're going to need regarding composing vs producing depends on the style of music you plan to create. Sometimes, certain parts (or works) of art ARE supposed to ellicit negative emotions, like horror movies or arguably harsh noise music.
Learning how to do all this does take time - don't be discouraged! If you don't assume you're going to make a living making music, you can take all the time you want.
Generally, there are two ways to publish your stuff: by joining a label (that puts out music with similar vibes to yours), or doing everything alone. My only advice regarding the former is: abide by the rules of demo submissions (if any are supplied) and don't give up. As for the latter, I highly recommend using Bandcamp for downloads, and a drop-shipping website for physical copies (unless you want to go 100% DIY). Kunaki & Trepstar drop-ship printed CDs even if you only order one copy! And Amtech looks like the go-to option for tapes/vinyl. You can even make your works available on Spotify and iTunes for free using RouteNote. Try looking for generic networking advices if you want to learn more (i. e. expand your knowledge on how to be consistent, how personal you should get with posting, how to get connected with your local scene, etc).
2. Freebies recommendations
-Generators - classics:
Kontakt Player, Reaktor Player, Synth1, VB-303, Dexed, TyrellN6, TAL NoiseMaker, TAL U-No-62, Surge, Arppe 2600, Zebralette, PG-8X, SQ8L, Eightysix, MonoFury, ZynAddSubFX, and everything by HG Fortune
-Generators - overlooked gems:
Vital, Freehand, FireBird, KairaTune, Cybermath, Oatmeal, Chorg PS-20, Mikrosynth, basic64 (poly)/basic65 (mono but updated), Helm, PolyGAS, T-Force Alpha Plus 2, MT Power Drum Kit, Sketching Orchestra, BBC Symphony Orchestra, Ample Guitar M Lite II, Steven Slate Drums Sampler
-Effects - classics:
Guitar Rig Player, W1 Limiter, C3 Multi Band Compressor, ReaEQ, Ambience, OrilRiver, Valhalla Super Massive, and everything by MeldaProduction, Tokyo Dawn and TAL
-Effects - overlooked gems:
Fracture, Hysteresis, Fragmental, TENQ, DFX Buffer Override, BowEcho, EasyQ, Cocoa Delay, ++bubbler, IEM MultiBandCompressor, and probably also everything by Dead Duck Software
Freesound, Ghosthack, Loopmasters, MusicRadar, Neurohop Forum, Prime Loops, Cymatics
3. Content recommendations
Adam Neely, 8-Bit Music Theory, Rick Beato, 12tone, Signals Music Studio, Interview: Jacob Collier (by June Lee), and also maybe Andrew Huang and David Bennet Piano if you feel like you really need even more
-Your DAW's manual!
-Wikipedia and/or plug-in/hardware manuals for glossary such as plug-in/gear parameters
*Composing/music theory (please read in this order - and keep in mind that theory is descriptive! I also highly recommend practicing with a keyboard/piano of sorts while reading these):
-"Music Theory for Computer Musicians" by Michael Hewitt (or "Composing Digital Music for Dummies" by Russell Dean Vines if you can't get it)
-"Music Theory 101" (and the rest) by Tuberz McGee (or "Open Music Theory" by Hybrid Pedagogy Publishing) as a recap (alternatively, the "Learn music theory in half an hour." video by Andrew Huang)
-"Beyond Functional Harmony" by Wayne J. Naus or "Twentienth Century Harmony" by Vincent Persichetti
-"Mixing with iZotope" and "Mastering with Ozone" by iZotope (it does help even if you're not a mastering engineer and don't use iZotope's software) or "The Mixing Blueprint" and "The Mastering Blueprint" by Cymatics, and "Ultimate Guide To Compression" and "Vocal EQ Cheat Sheet" (helps with non-vocal stuff as well) also by Cymatics
-"Mastering Audio: The Art and the Science" by Bob Katz if you need more after reading the previous ones
-Sound On Sound articles if you feel like learning even more
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