if this is ur 1st char then u would definely want to farm hall of pain. In case u don't know drop rate there is higher than many uber even duncraig, mostly rare or unique with <200 MF, this has been confirmed by many ppl including me. Get jitan charm, then find hall of pain wp, then keep clearing all enemies from there up to hall of nih, finally clear all 4 ways of hall of Nih. This usually results in ~10 tu's, atleast 4 sets, and 1-2 su's, plus u will get 2 signets of learning which u will need anyway. Repeat this until u get 500 signets (~150 - 200 times), in the process u will get tons of SU's and sets.
The point of farming this area is, beside it having good drop rate, u have a more reasonable reason to do it, getting 500 signets is always more important and stable than finding a full set. Plus, in the process, u get many thing u need for ur char: jewels and tu's into shards for jewel crafting which is very crucial for endgame casters; rares for gold; su's and set's; and the best thing is u will be able to practice facing elite monsters like uneslise lady, skull crusher, lightning monkey- some of the most annoying enemies in the game, while it's still ez enough to not struggle too hard. So after a few hundred runs, u have: necessery items, experience, and full stats points. I got like 2/3 of my su's from there. Don't think just a full set is gonna change ur life, though lightning set pretty much does that for a sorc, but what is more important for ur char is trivial things like socketting, ways to move/dodge mobs, and ur "feel" of that char, if u have only got her to 120, that's not enough to get used to her completely.
side note: Actually cold/light sorc can farm dunc pretty easily with tu's and rw's. also she can r@pe any (except kab) heroic. K3k shouldn't be a problem since skeletons are ez to dodge and balls die in 2-3 thunder stone. That's why i think u haven't get used to ur char completely.