FlamingDriscoll09, Change your Minstrel once you are able (a level in the game lets you do that). Paladin, the one I'd use, is only usable once you get to Gleeba, which will take a while. But becoming a Gladiator is also a good choice that can be done soon. All you have to do is recruit a Warrior and train it up a little bit in order to beat the quest.
The ideal party in DQ9 is:
Gladiator/Warrior
Paladin
Priest/Sage
Mage/Sage
Now you can't really unlock the Paladin yet, or a Gladiator. So I guess I'd just change your Minstrel to Warrior or a Gladiator once you unlock it, and change your Martial Artist to a Priest. Once you get a Paladin, you can then change your Martial Artist. Just try and get skill points in Shield and the skill that doesn't affect a weapon you won't be using for sure once you change.