I have a little experience in this area. I applied last cycle and went on several interviews.
My personal opinion is that everybody should invest in a nice black or grey suit (i prefer skirt suits, but whatever fits and flatters you bests works). I don't understand all this hate for the nice, classy, put-together look of a black suit. I purchased mine from Banana Republic and I loved it. I saw quite a few other girls wearing this same one too. It was a little pricey, BUT it is an investment and something you will consistently need throughout your career. Also, I got mine during a 40% off sale, so it wasn't too bad.
In many of my interviews, almost everyone (male and female) was wearing a nice black or grey suit with a nice colored button up shirt underneath. If you want to be an individual/creative, do it with your shirt color. Personally I think a nice purple, blue, light green or soft pink are all good choices. But don't go too crazy. I think the collared shirt is the way to go, but some girls wore simple blouses instead. A nice, simple pearl or gold chain necklace with matching earrings can also add a little pop. As for shoes, plain black flats or pumps were fine. This is what I saw in the majority of applicants.
There were always a few girls, though, who decided they wanted to be an individual and wear something a little different. In most cases, I think they just ended up looking underdressed and like they didn't fit in. The "sea of black suits", IMO, looked classy and nice, not boring. It looked professional with us all in the conference room wearing our business suits. Sometimes other things can look ok, but I think its too much of a gamble. In any case, what you wear probably won't make or break the decision unless its something totally outrageous. Just wear something that fits well and allows you to be comfortable and confident throughout the entire day. Wear something that makes you look like a future DDS/DMD.