If you're planning to play in zerg most of time, 48 rc 11 supp 22 dark is the best build, you can make it a bit different, but it's the base. Big personnal burst with bolts, 50% cold debuff for your own baseline DD, max'ed GTAE and glorious spears + one little NS to annoy solo'ers and gain long range ability to rupt.
Kobold for the race, by far, i like frostalf's skin but the race isn't that much of a great caster on the long run with higher RRs cause of that freaking 55 base dext and it's taller.