Is this fall/winter or spring? If it's fall/winter, you might be looking for something like dark wash skinny jeans/leggings and boots, a fitted shirt with a sweater/jacket/scarf over it. Here's an example:
How about a "uniform" scarf (scarves are huge up here)? It can be solid colored or even patterned (like a plaid that has your colors), or a mix. You can have the sorority's letters embroidered on them (or not).