going Dragoon clears all status ailments, also- Meru's Rainbow Breath is a cure-all. and did you know about the Virage boss in the Ruins? just solve the "Order of Evolution" puzzle...
My strategy (you'd don't have to take it to heart.)
Recommended party: Dart (duh), Meru (with Rainbow Breath dragoon magic), & Albert (with Rose Storm dragoon magic, and if possible Gaspless dragoon magic.)
Battle preparation: before you fight the Grand Jewel, fight enough to lower your SP to 2. you want it this low...
Getting started: SAVE AS MUSH MP FOR LATER!
start off with everyone going dragoon at their reduced levels, just attack normally with Dart and Meru and have Albert use Rose Storm- to reduce damage to anyone caught in the Staff's wake.
Keep fighting, and go dragoon before your SP reaches 3 to lure the Grand Jewel into wasting a turn using the staff. don't be shy when using Meru's Rainbow Breath or Albert's Rose Storm.
After it heals itself, the go ballistic with the Dragoon Magic... it's Earth-based, so Gaspless should put a dent in it...
Summary: Go dragoon to inflict extra damage, to lower your SP gauge, and to lure th Grand Jewel into wasting a turn. Heal via Rainbow Breath, and put up constant shields via Rose Storm.
The Grand Jewel is just a glimps of things to come... try fighting-
the Divine Dragon with the Dragon Block-staff in full and continuous effect! :eek:
good luck.