Have max hp and mp.
Must have Final attack on phoenix on at least one of you characters so you come back to life up to 5 times.
Knights of the round (not essential some people think it is)
Hades.
With ruby just cast hades on him and then his claws.
He will then be paralysed.
Hit him with KOTR and your most powerful attacks have one character ready to hit him wiv hades again befor he moves again. Have armour which absorbs fire and a ribbon.

Emerald is then easy as you will probably have mastered Final attack and phoenix a few times so every1 will have 5 lives.
Equip all ultimate weapons, 4x cut and at least 2 mastered counter attacks on every one and it will be easy!!
As each attack will take 4 x 9999 which = around 40,000
for one person!