It's always good to pick up some cheap basics to mix and match with your nicer clothes (like Coco Rocha and her Aldo boots - see Oct 4 post). Here are some good options from the Gap.
This pencil skirt is a classic cut and only $44. It has a bit of stretch in it, so if you're small it may actually fit. (it's really surprsing how many size 0 pencil skirts actually do not fit, I mean they're supposed to be tailored fit, not baggy) How can you go wrong for $44! It comes in black and terrain (color below).
I also like this long sweater from Gap's European Collection. $88. It's 95% lambswool, 5% cashmere. That's a nice blend, usually less expensive sweaters have some acrylic in them, which is not nice at all! Perhaps that's why it's a little more pricey... but still much less than a designer version. I would get black, but I'm showing it in gray below so you can see the detail of the knit.
I love the slouchy comfortable look. It would look good with skinny jeans, or you could dress it up with a skirt, heels, and some chunky bracelets.
Gap is also a reliable source for inexpensive tights. When it gets cold, I wear them all the time. It's good to restock every Fall for the season since they get snags etc. They're only $12.50 or 2 for $10 each.
Of course I would love to only buy Wolford tights, but at $52 each, that's a bit hard to take when you can get perfectly fine ones for $10.