Well, just enough Str and Dex to wear your gear, then allocate Vit and Energy somewhat equally. I usually go with more Vit, but its a judegement call.

Max Frozen Orb and put like 6-8 in Cold Mastery.
Depending on what you want to do, the choice is now up to you:
If you wanna do manual Meph runs, you should Max Firewall or Meteor and Max Fire Mastery so you can do the shot across the moat way to kill Meph.
If you wanna do some bot Meph runs, you should Max Nova, TS, and Lightning Mastery. I'd honestly say go with this build (Cold and Lightning tree), because even if you are gonna do manual runs, once you get the technique down of teleporting/dodging attacks from Meph, then attacking, you can kill him that way just as easily, if not faster.

Its up to you.

Edit:

Oh yeah, put 1 point in warmth, teleport, one of the cold armors, and energy shield, your gear should bump the skill points up plenty more after that.