Hellobee Boards

Wraps in general are very versatile. A 6 is a good base size for most people-- you can check the charts http://www.bwiaustin.org/wp/?page_id=425 for some additional information on that topic.
Favorite brand-- you can't really go too far wrong here. Pricing right now is pretty competitive on the swap, and quite a bit down from several months ago, so it's a good time to be a buyer. You might want to keep an eye out for hemp or linen blends, as those are typically more supportive, but don't feel tied to that recommendation. As far as the swap goes, best advice is to just watch for a while. Get a feel for what you like the looks (and price) of, see what seems reasonable as a price, and go from there. Pricing doesn't tend to be too out-there, because people know they won't sell for a wildly inflated price, but there are some people now and then who will really ask more than they ought, and it's nice to know what the going rate is so you don't end up over-paying. I'd be happy to help once you get a feel for what you are looking for.

Hemp and linen seem the most supportive to me.
Most importantly, get something you love There are some great deals on the swap right now.