Valid races IMO are
Humans: Always good.
Elves: With a vanilla enemy, Humans will probably win in damage over time BUT elves have the flexibility of changing into a Fireball strategy against Mana Burners and physical immunes, and also use utility glyphs better.
Though if abusing Mystera then you want to use...
Gnome: See elves, except more of short-term benefit if you know when to use your mana potions right. Paired with Mystera you can have your mana potions heal ridiculous amounts of mana which you can convert to heals.