Hello!
I found that a very easy way to level a sorc is to go with Cold/Lightning.
This way you can AoE your enemies very easy and slowing them down at the same time.
Start at lvl 2 to get Charged Bolts, this also is a good and mana efficient way to AoE even tho it dont damage that much.
at lvl 6, get Frost Nova. My favourite spell after Nova. Awesome damage and good slow. Keep taking Frost nova up to lvl 11.
at lvl 11 pick Static field in Lightning tree, as a prequisite for Nova.
at lvl 12 get, ofc, Nova, my all time favourite! Keep upgrading Nova til lvl 17.
At lvl 17, get Lightning as a prequisite for Chain Lightning at lvl 18.
Now at lvl 18 get Chain Lightning from the Lightning Tree.
Keep Going into dungeons aggroing as many creatures as poss. and AoE them down. Cash, item and XP reward is high!
This should help you get through the first 20 levels.
Hope this helped a little.
Have Fun and Good Luck!:wave: