If you are making exclusivly a fire lightning sorc, this is what i would do;

Lighting Skills:
Nova - Max
Thunder Strike - 1 at the very least, and let your + to skills do the rest. If you have extra points sink them in here.
Mana Sheild - 15 to Max (highly recommend maxing)
Lightning Mastery - Max
Total points used here - 67 if Msheild is maxed.


Fire Skills:
Pick either Fire Wall or Hydra with Fire Mastery Maxed.
Fire Wall Maxed with Mastery, points used - 42
Hydra Maxed with Mastery, points used - 44
Fire Wall and Hydra Maxed without any Mastery, points used - 46

Total allocated points allocated, 109-113. Obviously, u will have to use a judgment call as to when and where your going to put your points.

Again this is just my opinion.

FYI - there are only a possable 111 (i think) skill points available at clvl 99.