Your recruitment chairs need to make this process as easy as possible, but you have to respect their decisions as well. I understand some people being horrified by the thought of being told what to wear, but I mean you've gotta make a good impression, look classy, and uniform. We even told our alphas what to wear during their alpha period (each sorority did this during their pleding period, for example: Mondays bid day shirts and jeans, Tuesdays: pin attire for meeting, Wedensday: letter shirts with black, Thursday: free day, Friday: spirti shirts). When I was REcruitment Vice President, we had 4 days of parties and it was really easy. the first round, everyone wore their jerseys (every sorority at Baylor has the same jerseys in their colors, with their letters) and black pants with black closed toed shoes (november). The second, I had everyone wear khaki pants and we ordered black tshirts with ADP in animal print letters and they again wore black shoes. ON the third day they wore black pants and a fun, going out type shirt, but not hoochy momma looking. Finally on pref, everyone wore a black dress with black shoes. Hair and jewlery were all specified and all that. I made everyone bring the pants/shirt/dress they were going to wear a month before recruitment and i made them try them on. If their shirt was too slutty, they had to pick something else, if their pants were too tight or short, they had to wear something else. Saved some time during parties. they had a lot of freedom in what htey wore, but still looked uniform. that's how most of the chapters on my campus did it (as far as I know!).
My random .02