Hi Kimmi!
Sigma Kappa is at my school too. What school are you at?
Formal rush used to be only three days long here; so you shouldn't be worried about having only met the members three times before they gave you a bid. It's actually a lot easier to get to know a girl during COB.
COB was created so that chapters can fill quota or total. BUT they don't just start offering bids to anyone. They're still picky. It's just as special as getting a bid through formal rush.
The fact that you were comfortable with them right off the bat says a lot. Can you imagine how comfortable you'll feel around them a month from now!?
Whites=solid white dress, white hose and white shoes
If you don't already own a white dress, ask the chapter if you can borrow one for your pinning. Then ask a member to go shopping with you for one. They'll know exactly where to find a good selection.

Also, ask if off-white/cream colored is acceptable. Some chapters will let it slide and some won't.
There are lots of different types of Greek organizations. You could join a social, professional, academic, honorary and a service GLO.
We can answer all your questions to the best of our ability, but don't forget to utilize your Pledge Mom and all the actives.

They'll be the most accurate with their answers.
Good Luck! Keep us posted. There are a few unregistered Sigma Kappas that pop up on here occasionally, so keep you eyes open for them.
Feel free to email me with any other questions.