A black crew-neck t-shirt and khaki chinos are true menswear must-haves if you're picking out an off-duty wardrobe that holds to the highest sartorial standards. Complete your outfit with a pair of dark brown leather work boots to avoid looking too polished. This is a safe option for a neat winter-to-spring look. Off-duty combinations for 30-something gentlemen aren't actually that hard, as you see.