good build for a 19 mage... hmmmm, sounds like you'll be twinking it. Go pick up
this wand and go with
this build (putting the last few points wherever gets you off most) and that will be about the best and reliable DPS you can get for that level range (similar for a priest too). You'll have to respec if you level past 19 though, because past this level braket 2 points in Wand Spec are wasted talent points.