Always wear a good watch, no matter what if you are wearing a suit or sweats. A good watch will hold value over time. It's not about the brightest or the biggest diamonds, it's about quality mechanisms, the heritage of the company you're buying it from.
I own more pairs of Calvin Klein underwear than I can count. At any given time, I probably have 50 to 60 pairs on deck. I travel with an entire suitcase of underwear and t-shirts, and they're all Calvin Klein.