I don't know if there is a site just like gamiss but if you want to buy clothes with bitcoin you must exchange it first to $ and paypal as a payment method. Because most of the online shops do only accepts payment with paypal or any other authorized web site. If you are not unable to find some other site like this, well try my suggestion and use virwox for it.
Yes, of course. Not just clothes that I can buy with butcoin, any item I want if I want then I can buy it with bitcoin. But the problem is that there are currently no stores selling goods or services with bitcoins. so I think it's still quite difficult to shop with bitcoin so from that when wanting to shop with bitcoin then we have to exchange it first with currency applicable in that place.