So as you can see, looking casually sleek doesn't require that much effort. Opt for an olive blazer and a crew-neck sweater and be sure you'll look incredibly stylish. Puzzled as to how to finish off? Complement this look with a pair of dark brown leather desert boots to change things up a bit. We suggest this one if you're looking for a comfortable ensemble that's as stylish as it is functional. As a 30-something Millennial gentleman, you want to start dressing more like a mature gentleman. That's when combos like this are a surefire option.