The big, important thing about the circle of fifths is that the V7-I movement is the single strongest resolution in all of music. Anytime you play a dominant chord of any type ( 7th, 9th, 13th, etc. ), it strongly wants to resolve to the I chord. And then, you can "cycle" through them to set up lengthy jam opportunities, and still work back to the original key, and it will sound very good the whole time.
Here's an example, all the 7th chords are the V (5) chord, and the next chord will be the corresponding one chord of that key:
E7 - A A7 - D D7 - G G7 - C C7 - F F7 - Bb
Bb7 - Eb Eb7 - Ab Ab7 - Db Db7 - Gb Gb7 - B
B7 - E E7 - A
See how this will work through the V7 - I progression in every single key, and eventually return to the starting point? Now, to really spice it up, you can then add a iiminor 7th chord in front of all the V& chords, like this:
Bmin7-E7-A Emin7-A7-D Amin7-D7-G Dmin7-G7-C etc.
You will hear this, and/or the aforementioned cycle of fourths progression, all the time in jams, especially in jazz. A common device in jazz is "backcycling", where you concieve of your "home tone" ( ending point ), and then work your way back to it through cyclying through V7-I or iimin7-V7-I progressions.
Hope this makes some sense.
Out of the loop? I didn't know there was a loop!