Absolute skills

Demons (the only doubts arise regarding the perks in dark magic, but it's worth it), Sylvan (excellent starting abilities and nothing unnecessary in the upgrade process), and Necromancers (again, nothing unnecessary), and Orcs if you're planning a long game; I simply prefer a tent and a ballista to a catapult when playing. Although, I usually complete the entire map having only reached level 20 by the finale. There's usually no time for special abilities.