how to manage your mana while using buff as a bard?

[AskaRay]

So let say if my party doesnt have any magic dps nor a ninja do i still have to use foe in the beginning of the fight?

In these cases I usually wait a few pulls to see if the healer is bothering to DPS, if not then no it's not important.
Or, you can just ask them "you gonna DPS" that may get a faster answer, haha.