For Horde, the best race that offers WoTLK Gold any great benefit is Trolls for his or her Haste buff: Berserking. While Haste isn't the best precedence for Fire Mages none of the opposite races offer any advantage.
For the Alliance, Humans are generally the cross-to race for Fire Mages because of the moderate development to the Spirit stat with The Human Spirit. This mixed with Molten Armor...