We know the Circle of Fifths as a chart that spells the 12 Major/minor key signatures, but it can also help you play comfortably in all 12 keys!
Here are two approaches you can use with the Circle.
1. Learn to change keys rapidly.
Playing counterclockwise around the Circle will prepare you for root motion in 4ths, maybe the strongest chord progression in music.
Turn on your metronome! and play the C Major scale in one octave. Without losing a beat move to the F Major scale, then Bb, Eb, and continue around until you get back to C. Anytime you have problems figure out why. Is it a fingering issue? Review fingerings. Too fast? Slow down the metronome, if you were playing 1/8 notes (2 per tick) play 1/4 notes (1 per tick). If you ascend up the scale descend down too.
Use this method to practice your minor scales, Dominant 7 scales, or arpeggiate chords; triads, Major 7, minor 7, Dominant 7, inversions etc. Try different combinations in various parts of the fretboard to keep it fresh.
2. Learn a key more thoroughly.
A. Play the Major scale in two octaves with good fingerings.
B. Play the 7 triads (strum or pluck) I Major, ii minor, iii minor, IV Major, V Major, vi minor, vii diminished, close with another shape of I Major.
C. Connect the triads by arpeggiating through all 7.
When triads are easy extend to 7th chords, and work in inversions of chords.
With each practice session move to the next key. The design of the Circle gives you 12 sessions of Major, 12 minor (Natural, Harmonic, Melodic), and move around the 5 segments of the fretboard. Be creative, challenge yourself and the Circle of Fifths will keep you growing for a very long time.