[MC5C]

When I think of and play jazz chords, I think of three and four note chords, often with no root, and never in first position (no open "cowboy" chords at all, ever). If I play no root, that is because the root is implied by the harmony - like a V chord in a II-V-I sequence that I play as 3, b7, 9, 13. I focus on three and four note voicings because I can add a root bass note on the 4, 5, 6 strings pretty easily if I am playing chord melody. I probably focus on a few voicings, maybe three or four for each type of chord, and I substitute a lot. I may do a b5 sub for a 7th chord, Maj7 or Maj6 or even a 6/9 for any major chord, m7 for any minor chord, 9, 13, and all sorts for dominant 7 chords. Sometimes the melody drives the choice, many tunes have a b9 in the melody over a V chord, so I play a 9b5 chord instead of a Dom7 chord. It's been said that well over 50% of classic jazz tunes, particularly in the bebop era, were over blues changes of some sort or rhythm changes (I got Rhythm) so just learning some ways to comp through those two tunes is a great start.

One other thing - if you are playing from a fake book, keep in mind that a lot of those chord call-outs are way over complex and not needed. Look at the melody note, the chord position and play something that fits. Like if you have to play a II chord, that's minor and you can play almost any minor chord you feel like as long as it has a b3 and the other notes aren't closer than a full tone to the melody note. One other other thing. Often in jazz you leave a lot of space. If you have a II-V-I sequence over four bars you might play the II for a half note then rest, just pop the V for an 8th note in the second bar, and comp something interesting but sparse in the last two bars.