Playable races resource overview in brief:
Humans get the most gold production.
Monsters get the most food production.
Undead get the most mana production (and use it instead of food).
Arethi Elves (with DLC) are good at all the above (but not best) and can also get the most research.
Planestriders (Warlock 2) are a mix of the 3 main races.
Svarts (Warlock 2) specialize in research.