Here is an effective way to memorize the circle of fifths and all of the II-V-I progressions. And doing your best to achieve the highest score on each drill adds an element of fun.
The circle of fifths drill gets progressively more difficult, leaving more and more chords missing until you are recalling the chords purely from memory. You can drill yourself on the circle of fifths with either major chords or the relative minor chords.
In the II-V-I drill you must identify the missing chord as you try to accumulate the highest score.
In either drill, you can choose whether to view chord name incidentals as either all sharps or all flats.
You'll never regret mastering this bit of musical knowledge!