Should i fight Gilgamesh. My main party is

Vaan Zodiac Spear 5500-6500 damage
Ashe Katana that causes poison 1500-2000 damage(I think)
Balthier Perseus bow parallel arrows 1000-2000 damage(I think)

Ashe uses mystic, Vaan heavy, and Balthier light

Vaan uses pure attacking and thats about it so I use no gambits
Ashe is my main mage and heals people but i should put buffs on her gambits
Balthier is my back-up mage and ranger, also no buffs but i should add them

They are all around level 52
Second party only good enough to heal main party
I know to take the dog out first

The reason i am unsure about some damages is I havent played for around a week