33girl, that reminds me...my little sister's white dress was initiated into AGD, Alpha Phi, Tri-Delt, and I think DG. Too bad she didn't know any KKG or Pi Phi new members that needed to borrow dresses, or else it could have gotten into initiation at every sorority on campus that semester!
I got my white initiation dress on clearance for I think $5 because it had a big ink stain on it. A little hairspray cleared that right up! I got a lot of mileage out of my dress because I wore it for a few initiations and two Halloweens. One year I was Baby Spice (it was really short and skimpy...I wore a sweater over it for initiation) and one year I was an angel. I now have a more appropriate white outfit for initiation because I figured I should set a good example, being an advisor and all.
The two pieces of initiation clothing that were the worst I've seen were when one of my sisters wore a long white t-shirt and when another wore white flip-flops because she couldn't find white shoes.
You should talk to your sisters about getting seniors and alumnae to donate their old white dresses to the chapter so that your new members don't have to scramble around trying to find white clothes in the middle of winter. My chapter started doing that this year and it's a really good idea.