For something more on the casually cool side, consider this combination of a dark green short sleeve shirt and a crew-neck t-shirt. A pair of black leather derby shoes immediately ups the classy factor of any outfit. So as you can see here, it's a knockout, not to mention spring-ready, look to have in your seasonal rotation. Gentlemen wondering how to sport semi-casual outfits as you move through your 20s, this getup should answer your question.