I feel your pain. As a female in a high-end architecture firm - where you're expected to design yourself in addition to buildings - it's a challenge.
But I'm working on it! For the past few years, I've been whittling my wardrobe down to black, white/ivory, grey, and olive-y greens. I've found specific brands of pants that fit me well and last. I've pared my necessary shoes down to 2-4 styles per season: 1 pair of black heels, 1 pair of neutral/buff heels, 1 pair of black flats or sandals (depending on season) and 1 pair of neutral/buff flats or sandals. I've also moved towards a "minimalist" style of dressing that doesn't tend to get too dated (think Tilda Swinton).
Weekend wear is actually the most challenging, for me, particularly since I dislike dry-cleaning stuff that I don't wear to work. Solution: jeans, solid t-shirts, fantastic jewelry, and red lipstick. Done.
It's taken some conscious effort - and research to pin down how I wanted to look before I began weeding out the old and adding in the new - but it's working, and I'm slowly getting there!