Best type of mailer to ship clothing?

I'm gonna be selling some of my clothes on eBay and wondered about the different types of mailers to purchase. I've looked on-line at poly mailers/poly bubble mailers, and Tyvek envelopes. Those poly mailers look like plastic bags and I'm wondering if they're good enough and sturdy enough to ship clothing. Will the clothes get wet inside them? The poly bubble mailers look better but more expensive. And the Tyvek envelopes are advertised as being strong and water-resistant but again, pricey. I'm looking to buy in bulk on-line(like some 10x13 ones) and most of my clothing is light- men's shirts so I think I can do it First Class. And once I've decided on the type of mailer, do I wrap the shirt in anything to make it look professional? Or put it in another bag to make sure it stays nice? Advice would be appreciated...