Master Gizamaluke only has one attack that targets all of party members, Water, but it uses it fairly often. Gizamaluke uses Silent Voice to counter any offensive spells against it, inflicting Silence on the target.
Vivi should cast Thunder, and can use Focus to increase its power. Vivi can also use Slow to decrease the rate Gizamaluke attacks. If Quina is in the party s/he can use the Mighty Guard, which can be learned from the enemies outside Gizamaluke's Grotto.
If possible, the player can use a Tent on Gizamaluke right at the battle's start, as there is a chance it will inflict Silence and Blind. There is also a chance it will fully cure him, so it is best used as soon as the battle starts as the battle can be troublesome for underleveled or inexperienced players.