This combination of a grey long sleeve t-shirt and navy chinos is on the casual side yet it's also stylish and really sharp. Go ahead and complement your look with a pair of black leather derby shoes for a sense of class. When it comes to dressing for fall, nothing beats a kick-ass getup that can take you from season to season. If you're often not sure how to dress as a 20-year-old, this outfit is a practical illustration.