hey basically if you want a style exactly like hers your going to have to fish out some cash, however I have a few suggestions for you :)
La Senza have a sale on right now, you could probably find some nice suspenders, a garter or two, fishnet tights, stocking, maybe even a basque with Taylor Momsen written all over it, this will give you the sex edge to rock up anything you wear. you also might like to try Anne Summers because They have full body fishnet jumpsuits and other stockings and accessories at a reasonable price.
Also try Primark, I know its cheap and nasty, but if you get a vest top that's 4/5 sizes too big then you will have an excellent start on half of her clothes, if you want you could buy some fabric paints and splatter them over the shirts, make them unique so there not just Primark trash. also buy some plain black underwear form here, if your going to be showing of your crown jewels you don't want anything too racy or childish.
look for fashion tights anywhere you can and maybe rip them up a little, generally Dorothy Perkins and H and M are good places. and search around for neat little accessories (Claire's do do some okay stuff but its stupidly expensive for what it is)
and remember to muzz up your hair with back combing and hair spray
basically have fun and wear with confidence =)