One of the first theory lessons I like to teach is that there are only 12 major chords and 12 minor chords.
Learning these is attainable in a relatively short amount of time.
To simplify this further I start with the six "3 White note chords":
C, Dmin, Emin, F, G, and Amin
And the six "White-Black-White chords":
Cmin, D, E, Fmin, Gmin, A
With these second six we start to have the potential for some unusual and more offbeat chord progressions.
The remaining chords can be thought of as "black-white-black" (6), "all black notes" (2), and "irregular shapes" (4).
I encourage students to write some chord progressions using these first twelve chords. Below is a page of progressions I wrote to play around with.
Try them in the octave around and below middle C with your right hand and double the bass note an octave or two lower in your left hand. Put on a drum beat or a metronome and loop them several times to get the big picture sound of each one.