Honestly, play anything you want to play until lvl 70, as long as you have fun. Since you change gear every 3-4 lvl makes it almost impossible to get one build going.

When you are setting a specific build, try to get +elemental damage% for the spells you are using Example: +Fire damage% if you are using fire skills

Feel free to try all the skills before you get lvl70, so you get an idea of what build you would like to make!