A grey sweatshirt and a denim shirt are the kind of a no-brainer off-duty combo that you so terribly need when you have no extra time. To introduce some extra flair to your outfit, introduce a pair of black leather casual boots to the mix. This one is a viable idea when it comes to piecing together a kick-ass outfit for summer-to-fall weather. Wear this outfit to pull together a more mature look as a guy in his twenties.