Invest in Classics
I like to use the "would a French girl wear this?" test on my purchases. Typically, if the answer is yes, I know I won't be unhappy with what I've bought a year from now. I try to avoid most trends. Invest in quality, and buy timeless pieces. You will not regret it. And then shop the closet!
Vintage is the best! You can build a wardrobe of lovely pieces without adding anything new to the "demand" side of the equation. The bonus is that secondhand items are typically much less expensive than new ones. As a petite girl, I appreciate this since I often need to have my clothes altered by a tailor.