This is a really interesting and fun exercise.
First things I would get: Black leather jacket and black knee-high moto boots, preferably with a front lace like the ones I have. The jacket is something I've always wanted, the one I have now is SUPER CHEAP ie not good quality at all, and the boots are absolutely essential to my personality.
Next up would be a couple pairs of good skinnies - dark wash and black, most likely. At least one colored pair would be nice. One black pencil skirt and one swingy A-line skirt in navy. Probably a pair of black or gray dress trousers, straight leg or bootcut. I have been liking my bootcut jeans more lately, so I'd want at least one of those too.
Shoes - a basic black pump and a pair of black flats, and one colored heel maybe red. One pair of slip on or Converse-style tennies (but not Converse brand, because they are owned by Nike and we don't buy Nike in our house) for weekend wear.
Tops - this is probably where I have the most trouble defining my style. For work, I'd need at least a couple button downs in black and maybe another solid color, plus a cowl neck sweater - I really like those. Maybe a couple solid color long sleeve tees, v-neck preferably, in black and purple or red. I would SO miss all my band tees, so I'd need to replace a few of those. Also would need some basic tank tops for layering. Have to have at least one corset! I would actually prefer an underbust, which I don't have yet - black of course. A fitted black cardigan, and a long drapey one maybe in gray. At least one jacket would probably be a good idea.
Dresses - I would want at least one wrap dress, one sheath dress, and one vintage style wiggle dress. A floral cocktail A-line style dress would be awesome too.
Finally, I'd have to spruce it up with at least one item of each print: leopard, houndstooth, plaid, polka dot, black and white stripes, and floral. Could be pants, skirt, top or accessory like shoes or a scarf. Oh, and a skinny belt small enough to use at my natural waist.
Interestingly, most of these are things I already have, but a couple things I don't... so now I'm off to make sure those are on my re-focused shopping list!