Learning the circle of fifths (or camelot wheel for dj's) is one of the most important pieces of theory a beginner musician can learn. If you run scales, chords and arpeggios though the whole circle enough, you'll be able to play comfortably in any key. It's also a good idea to always run the circle with both major/minor scales.

For some reason I'm picturing Beethoven holding a score above his head with both hands while standing on a cliff, 🎶The circle of fifths . . .