This relaxed combination of a denim jacket and a dark brown crew-neck t-shirt is a goofproof option when you need to look great in a flash. And if you want to immediately dress down your outfit with a pair of shoes, complete your outfit with dark green canvas high top sneakers. As this combination proves, you can't think of a better pick for warm weather. Casual getups for stylish 20-year-old gentlemen aren't actually that hard, as you see.