Both races Elf and Dwarf are good for this build. The Elf has slightly better perception and more magic resistance, while the Dwarf has better physical resistance. The Ranger Guild's perception combined with the race's makes them the best combinations for exploring and detecting traps. Additionally, they can Tank if specialized in Protection, and can cast Levitate on the entire group.

Thief is especially useful for acquiring more gold at the beginning of the game thanks to their passive ability Plundering. They can also open magically locked chests. You can specialize them in Combat for more damage, or in Dusk for greater combat resistance. The alternative would be a Ninja, though they don't have the Plundering ability.

Paladin is the most versatile class in the game. They'll help a lot with their auras, but also have healing abilities for the group. You might want to specialize them in Combat to improve physical damage, or in Holy to enhance healing. As an alternative, you could use a Shaman, which is also a class with support buffs and group-wide healing instead of single target. You could use a Cleric instead if you want to maximize healing.

Mage is the class with the most powerful damage spells. Specialize them in Fire for even more damage. If, instead of focusing so much on damage, you prefer supporting the team with buffs, you'll want to choose a Warlock instead.