My idea set up is

Vaan - Zodiak Spear - With battle harness and Genji Armor for a good counter attack rate.

Bathier - Sagittarius bow, Artemis arrows or sometimes I perfer Assassins arrows for the Ko'ed effect. I have him with Cat ear hood too for fast speed.

Fran - Main Gauche, Zodiac Escutcheon, and jade collar for good evade. (I got her gambits with Foe *element* - Weak - *element*)

Basch - Masamune / Genji Gloves. With every other thing increasing strength to 99.

Ashe - Tournesol

Penelo - Wyrmhero blade

I have yet to find a good combo with Ashe and Penelo.