Depends on how much I like the chord :P
The -9 chords with 5th string roots were really easy for me to learn since I loved that chord when I started playing jazz. Some 7th and -7b5 chord inversions I'm still learning because I don't really like that much and I've found other extensions/substitutions that I like the sound of better. For 7ths, I started playing 13ths, 9ths, b5s, and diminished subs instead of the plain 7th inversions. For the -7b5s I've found the -7b511 (same as a major lydian voicing) and I like the simple root position 5th string root voicing.
But right now I'm working on an exercise my teacher gave me which is really useful to find fun chords and learn them easily.
Pick any ii V I vi progression (any key). Say you pick C, so start on your D-7 (any inversion) and voice it on strings 1234. Make the chords top note go up only chromatically, or if there's no way to make it go up chromatically (say you end up having the 3rd or 7th on top), have it stay in the same place. It's a really useful exercise for voice leading and learning new chord extensions or alterations.
When you've done this in enough keys (by enough I mean all

) try it on strings 5432, or 5321, or 6543, or 6432, ect. You can also try making the top note ascend by a whole step, thirds, ect.