Just learning notes isn't very advanced, so I guess you mean music theory? As a musician, you already know the 12 notes I assume?
Since I'm a big fan of Dave Stewart and his work with Hatfield and the North and National Health in particular, I bought his two little books on music writing and composition. The first one is this:
It's pretty good and breaks it down in a simple way, so that's something you can get.
Something else you can do is get some stickers for your keys, like these:
Those little suckers tell you what notes they are and what they look like in standard notation, expressed as quarter notes in the picture above.
Even if you know the notes, which you probably do (?), it can help you become more aware of what notes make up various chords.
The circle of fifths can also be an interesting way to learn a bit about keys and intervals, specifically the fifth. Something that I like about it is it's easy to just print out and place on a piano stand, which is something I did and why I mention it specifically here.
So here, you can see C sharing the space with Am. What this means is if you're playing the keyboard, you can use exactly the same keys and chords to play in the
key of C as in the key of Am. If you play the keys/notes C, D, E, F, G, A, B, C on your piano, that's a major C key. If you just start at A instead, it's the minor A key.
C major key
A minor key
.. So even though they contain the same notes, just starting from C will make it sound happy and starting from A will sound sad. Weird, huh?
Treating the letters in the wheel as notes, then going to the right on the wheel, you find the note a 5th above. So C's 5th is a G. These are notes that have nice dynamics and play well together. If you play a single note on a piano, its own note will of course ring out the loudest.. but the second loudest harmonic you will hear buried underneath it is a 5th. Hence, fifths are of special importance, at least in western music.
If you treat the letters in the wheel to mean keys, then the key of C major and the key of G major only differ by one note.
Key of G
Instead of an F (like in the keys of C / Am above), it has an F# (F sharp).
The further away down the wheel you go, the fewer notes are in common - until you start to get close again. F major key is also just a note different from C major.
You can use the circle of fifths for various things, like planning key changes. If you change from C to G, that's gonna be a gentle sort of change. If you change from C to A or E, the effect is going to be more dramatic - perhaps too much so depending on what you're attempting.
And then lastly, there's PLENTY of learning material available for free on youtube and elsewhere. Look up some of these concepts I've mentioned, like the circle of fifth, musical keys, chord structure or intervals or notation and you'll find plenty.