Based on the weapons I got and the choices I made early on, I've ended up with some cool effects but some that I probably don't need. Here's my setup (it worked okay but I'm open to trying other effects on my second playthrough.)
Harvey
Crit 91 Poison 79 HP 100 Sleep 100
Amelia
Crit 48 HP Recovery 50 Steal 63 MP Recovery 55
Lucile
Crit 58 Steal 50 Paralysis 52 HP Recovery 74
Olivia
Crit 50 Steal 100 Paralysis 58 INT 56
Also, all 4 members have an Accelerator Jewel, Harvey and Lucile both have the All Jewel, and Amelia has a Metal Jewel and Olivia, a Box Jewel.
Now, my first thought is not everybody needs Crit, only one person needs Steal (although really it's not needed, it's just one I like to have), only one person should have Paralysis.
Also, in looking back it seems like HP Recovery on all could be helpful, but MP Recovery might be even better (since I used a LOT of magic in the game.) I will say that Olivia's INT boost made her magic attacks AWESOME!!

I generally don't have a plan at the start of the game for what effects I want; I just take what comes along and make the best of it. But I think I could have made some better choices, that would have made the final dungeon/boss much easier. (I had to beat the final boss on Easy mode - mostly I'm sure because I did not plan it out, analyze all my available skills/magic, etc. But a couple bosses use Dark Inferno, which sets everyone's HP and MP to 1, so in that case HP Recovery and MP Recovery would have been really useful...)
Anyway, what does everyone else like or use in their party?