To don a casual ensemble with a twist, wear a dark green crew-neck sweater with a long sleeve shirt. Let your styling sensibilities really shine by completing your getup with black leather chelsea boots. While it can be tricky to stay on-trend in the dead of winter, it's combos like this that prove it's quite doable. As a gentleman in his 30s, you probably want to start dressing like a grown-up. That's when combos like this are a fail-safe option.