You're not alone, B2Y.
It's not been easy (or quick enough....for me) but I think I've finally tamed the beast of "spontanious purchasing".
If I'm online - which is really the only way I shop anymore - I put what I
think I need and want in my cart. You can save the cart so that when you go back to the site the items you chose are still in there.
Then the game begins. I wait a full 24 hours before I actually buy anything. Nine times out of ten when I go back and view my cart I'm appalled at the stuff I've put in there. What on earth made me think I needed all these things? It must be somewhat therapeutic to do this, though, because I enjoy picking out the items and putting them in the cart but I get more enjoyment out of deciding
not to buy it all and knowing that I've made a smart decision. I'm trying to downsize.....and I've actually become somewhat of a minimalist. Like you, I don't need umpteen different outfits to choose from.
Try making a game out of it. A challenge. Shop all you want and fill your cart as much as you want. Just don't click that "pay now" button till you've cleaned out your cart!
P.S. Try ebay. You can get great deals on brand name things there.