I like to compare learning and playing music to that of learning a language and playing a sport.
We've all heard that learning music is like learning a language. To learn a language it's helpful to learn grammar, and in music, it would be helpful to learn the music theory - scales, chords, and rhythms.
I also like to compare playing music to playing a sport and I think of playing a song would be the equivalent of playing a game. I then think of professional athletes and how they practice. Do they only play games when they're training and practicing? No. They do warm-ups, weight training, cardio training, run plays, scrimmage games, and many other exercises to prepare for a game. I like to practice music in a similar way and I think you can advance faster and have a deeper understanding when you learn more than just songs. I'm sure you'd agree that if you want to start improvising or getting into more complex harmonies and rhythms, knowing some music theory and how to practice it will definitely help.Notes and chords - what notes to play and what rhythms.The chords of the major scale (triads and 7ths) and some basic rhythms are a great place to start. It's a fun and creative way to practice and will build a solid foundation to build from. Check out these two images.
I like to think of the chords of the major scale as the chords of the song. Play each chord for 1 bar, 2 bars, or sometimes just 2 beats each. I try to be musical when I practice it. I think of time and rhythm, articulations, dynamics, sound, technique. I practice it at different tempos and in different keys.Here's a video showing how I practice this - https://youtu.be/TGWdE_7H0o8