Don't wear a business suit. Check with the Office of Greek Life at your school regarding appropriate attire. Generally, recruitment gets progressively dressier, so think about wearing sundresses and then something you might wear to a graduation ceremony or nice dinner-type event for video/skit day and prefs. As long as you look your personal best and your clothes fit you well (remember: you are dressing for the girls, not boys!), it doesn't matter if your clothes come from Banana Republic or Old Navy. See if your parents will pitch in at all for one nice dress that you can wear again, though. And check out summer sales at the department stores. It is amazing what you can find on sale!
Best of luck at recruitment!