A crisp black oversized dress shirt will do it. This shirt has been the most versatile item in my closet and I got it for, like, $6 at a thrift store. In Puerto Rico's 70 degree weather, I left the top three buttons undone for a relaxed vibe but kept it cool by tucking it into black jean shorts (yes, jorts). I finished off the look with black monochrome Dr. Martens.