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.
Cool, someday everyone will use bitcoin to buy anything. just wait. When it has happened do not let us be spectators only. Immediately buy bitcoin or get from the results of trading, mining etc. 
Bitcoin is only good to earn money but it is not too good in buying some items using this currency.
A currency can never be good if you can buy things from it. I guess you have wrongfully perceive bitcoins. Bitcoins are easier to spend where they are accept. Sometime the transactions takes larger than usual but its ok.
time and fees. its given that people will prefer to use fiat.if buying clothes is through online it is a good idea because bitcoin is suitable on online
transactions. Secondly i agree that bitcoin is not just for earning. it is a money. it can do things that fiat also does.