It depends if you will be able to get or not the cash skills.
You can get all attacks from the basic tab and the teleports, berserk and HP converting from the general tab. And that leaves you to a choice: You an only have a complete set of Free skills or Cashed skills. I only have the cashed skills, and i can recommend some: Glacier Circle, level 2. Its Incredible. Stunning Impact level 2 is also a great skill. Gorgos Flame level 2, Dark Whisper are also worth it. About free skills, i would recommend invert gravity level 2, stone curse level 2, paralyzing ray level 2. Thats all i really know about the free skills. Oh yeah, and i don't regret unlocking everything. Not even a little bit.
Protected by the gods... SIEGHART