The best place hands down in my opinion for Music Theory is Rick Beato's channel. I went straight from Music college into a Guitar Tutoring job and his videos have legitimately helped me earn my living! (Much better than where I studied!
)
I'd start with his video:
Rick Beato - (Basics of Music Theory)
This one is brilliant too:
- This isn't Rick but this is how to know your Major Scales form memory without your Guitar - super useful!
You really want to have a rock solid grasp of the basic stuff before you go onto learning anything more complex, just because the more 'complicated' stuff requires solid knowledge of the basics to understand.
The basic theory that helped me at the start was:
1. Knowing all 12 Major Scales off by heart.
2. Knowing the names of Intervals in the Major Scale & what happens when you flatten or sharpen them (what they would then be called etc)
3. Understanding which chords make up a Major Key and knowing the Triads & Seventh chords in each key.
4. Knowing the Modes names off by heart and how they relate to the Major Scale & Each chord in a Major Key.
All of this info and a whole lot more is sitting in Rick B's youtube channel. Some coffee and a notepad and you're good to go!
Hope some of that information helps and hope you're well,
If you have any questions feel free to ask!
- Chris