Hi man, well the arcane blast.. in "real combat" it is usually used only once.. then it has very nice dmg/mana ratio. I think one of the best. 195 Mana, 648 to 752 dmg an it does crit for ~1900 with about +490 spell dmg. However things change when you cast it more than once.. it is mana ineffective like hell. After 1st cast it goes up to ~457 something.. for this you can have almost 2 frostbolts (270 mana each, rank13 talented) with guaranteed around 1000 dmg each or 2000 with crit with same spell dmg. So there is basically no need to use it if you are frost or fire mage.
For leveling go with fire. You will not have the +dmg gear to make frost faster killing then fire. And the slow down of frost is not very use to you unless doing twink for PvP.. but this is not your case I assume. (you would not ask how to level the fastest way) Arcane.. at the moment this is mainly "end game support" tree. You invest points when allready @ 70 to have more mana (and regen) I would recommend puting some points after lvl 40, not sooner. Just check one of the PvE fire/arcane builds in the "Greatest mage post ever" on this forum.
I hope this helped.
Peace