Thief

Key 4
Stat Bonus Agility +10
Ability Less likely to be caught when using Steal
If you don't like dungeons but want to play an effective Type, the Thief is the way to go. Stealing may not be ethical, but it sure saves a lot of money. The exact mechanics of stealing are unclear, and it seems that at high Agility scores the Thief's bonus may backfire, but early in the game when it's really needed, it's a godsend. If nothing else, the ability to Steal Food will make your life much easier.
Compare Thief to other Types
Wizard

Related

Thief

Key d
Special Ability
Less likely to be caught stealing
Stat Bonus
Agility +10

Thief

Number 4
Special Ability
Twice as proficient at Steal and Unlock
Stat Bonus
Agility +10

Thief

Key T
Sprite Thief
Steal/Disarm Full
Thieves have very few Armour choices, though their Weapons aren't terrible. If nothing else, Thieves can use Bows, which remain worthwhile until the end of the game. However, Thieves are the only Type with full skill in steal and disarm. If you love robbing people, you'll definitely want to bring a Thief along. They're useful in dungeons for opening chests safely and avoiding traps (though they need to be in the front of the party for that). Because of how steal and disarm work, you really only need one character with the skill—if you have a Thief, you don't need to include any of the hybrids in your party.

If you don't intend to resort to robbery, and plan to use the dungeon maps in this guide, you can definitely get away with having only some steal and disarm. The Ranger is a powerful option, but all of the Types with that skill are worthy.