Most people finish the game around level 50, give or take 5 levels. By level 20 (or even 10) you should have a much better idea of how to build a good character to suit your playing style. I certainly did a better job in the game at the beginning compared to playing the demo.
My first time in this game and I expect to finish it around 42th level (I am 39 and have killed two mages of inner ring) and with soem luck I made an excellent character (warrior in normal level). I keot my skills till 12th level(and for that it was very hard at the begining) but then I invested them all in defense and offense kind of skills and strength (I got the mana and life from charms) and it worked out all right <img src="/ubbthreads/images/graemlins/smile.gif" alt="" /> The advices given on load and save screens are quite good heed them <img src="/ubbthreads/images/graemlins/tongue.gif" alt="" />
By the way I don't know if anyone noted this but the mana and the required levels are not noted on magery skills.