I would say that both TeamEstrogen:
http://www.teamestrogen.com/default.asp
and Terry:
http://www.terrybicycles.com/product.html?c=Apparel
have the largest online assortment of women's cycling clothes and gear.
They also both have excellent customer service. If you have doubts, just call either of them and knowledgeable women will cheerfully and patiently help you on the phone with your questions about cycling clothes.
Be sure to watch their sale sections periodically too.


Better to buy one quality pair of chamois padded shorts than to buy 2 pairs of cheap ones. As for tops, I just wear something really bright so that cars will see me.
I think helmet, gloves, and padded shorts/tights/capris are the 3 most important items. Unless you never ride more than 10 miles, in which case you might not even need padded bottoms.