Any recommendations for a beginner? I can read notes (though I'm practising that field too), but I really want to increase my knowledge of music theory.
Keep practicing note reading, and get as good as you can with it. This comes from a largely self-taught musician (at least until the seventh grade, when I took beginning instruments, and learned how to read treble and later bass clef).
So, until the seventh grade, I played everything by ear.
However, with regard to your question about increasing your knowledge of music theory as a beginner:
Before the seventh grade, I bought a book on piano chords, and learned every kind of chord in the book, in most of the keys (e.g., major, minor, dominant seventh, minor seventh, augmented, etc.). Throughout high school, I played in the band, and continued to learn more music theory on my own.
Later, at UCLA, as a music education major, my theory knowledge and capabilities were well rounded out.
However, as I learned before college, a person can learn specifically what you want to learn about music theory, largely on your own. May I suggest that you search the Internet for a site which is offering a practical, no-nonsense e-course or book about music theory for beginners. Then, if you like it, invest in it, and learn those things about music theory that you specifically want to learn at this time.
That's what I did until UCLA.