If you prefer contemporary pairings, then you'll love this pairing of a navy crew-neck t-shirt and white jeans. On the shoe front, go for something on the casual end of the spectrum and complement this look with navy and white canvas high top sneakers. So as you can see, it's an on-trend, not to mention spring-friendly, combination to keep in your transeasonal rotation. Now that's how you dress casually as a 20-year-old gentleman.