Simplest way to play a I-vi-ii-V in the key of C--
1. Chromatically target the G--P5 of the I and m7 of the vi.
2. Chromatically target the F--m3 od the ii and m7 of the V.
3. Going back to I? Target a half step down to the E, the M3 of the I.
Instead of all those modes, scales, esoteric Greek names, you have 3 simple notes to practice on G to F to E, a measly 1.5 steps. Play whatever you like that sounds good and, more impotently, is rhymically interesting, but when the applicable chord change happens, land on those notes.
I know this may sound TOO SIMPLE, but hey, there's only 12 frictin' notes in play to play.
