Button downs (especially oxfords) with very dark wash, slim-fit jeans and brown leather or canvas shoes seems to be what the more fashionable of my coworkers all wear. You can put together a full week's worth of these kind of clothes for about $300 without any sales and with only a few hours invested. I'm just getting started on this fashion project myself (at 28, I've wasted so much time), so I'm not an authority, but that's what I've been observing so far.