For a look that's very straightforward but can be styled in a great deal of different ways, choose a mustard polo and jeans. Our favorite of a countless number of ways to finish this getup is a pair of black athletic shoes. So as you can see here, it's a kick-ass, not to mention spring-friendly, combination to keep in your transeasonal rotation. Gents who are curious how to rock modern casual outfits as you progress through your 20s, you have your answer.