water wit, earth knghtmage/wit, fire killer, fire wit.dd
It doesnt matter which type of chars should get the pet since they'll be in a full team.

My team is kanako, venus, niss and xaolan. You can be versatile.
Kanako is for being the tank and healing anyone hp/sp throughout the fight and not wasting anyone else turn to heal.
Venus is sealing. It hits 2 targets and last 3 rounds(same as terra)
Niss is for the damage dealing. I just like her. Any human pet can be a damage dealer because of brooch but i just prefer niss. Fred does better dmg but its up to you.
Last is Xaolan for the stonewall. I keep her stonewalling others all the time and it helps venus survive. useful for JS/DS

Mainly a quest team for pets just need a dmg dealer, a sealer, tanker/healer, and Xaolan.