How to Recruit Goowain - Dragon Quest 6
Goowain can be found in the courtyard of Howcastle which is found in the southern portion of the Real World. In order to reach Goowain you'll first need to obtain the Magic Key from the King of Howcastle, you'll receive this item as a reward for helping his son Prince Howard complete the ritual in the cave. For more information about this check out Chapter 5 of my Walkthrough.
Note: He is not available in the SNES (original release) of the game; only in the DS and Mobile remakes are you able to recruit him to your party.
To reach the courtyard with Goowain you'll want to go down into the Howcastle Basement and up the staircase in the upperleft hand corner of this area. You'll find yourself in Prince Howard's room, which we had to visit earlier in the game during the main story. From this room go south out the door and you'll find Goowain in this courtyard.
If you're having trouble locating Goowain or figuring out where to go, use the screenshots on this page for more guidance. Or check my Magic Key Side Quest Guide; the first location on that list is for Goowain.
As far as Vocations for Goowain go, you should master Priest on him as early as possible to unlock the Fullheal ability. If you plan to do the Slimopolis Side Quest with Goowain you'll need this ability. Once you've maxed out Priest the other 3 Vocations that I strongly recommend are Gadabout, Dancer and then Luminary.
The Luminary Vocation gives you +15 Style when you master it and 15% more Style while your character is that Vocation. If you plan to do all of the Best-Dressed Contest Side Quest then you'll need to get as much Style on Goowain as possible for the Sage's Stone prize.
Vocation Permanent Rewards
These are the passive & permanent rewards that you will get when mastering a Vocation. You'll keep these boosts even when switching to a different Vocation. Once you reach level 5 in every Vocation you'll receive a Gospel Ring from the priest in Alltrades Abbey as well which will allow you to avoid encounters. You do not need to reach level 5 in every Vocation on 1 character, it can be done on multiple characters.
Gladiator: +20 Strength
Armamentalist: +20 MP
Paladin: +20 HP
Sage: +20 MP
Ranger: +20 Agility
Luminary: +15 Style (or 20)
Hero: +40 MP
Dragon: +20 Strength
Liquid Metal Slime: +100 HP