A crew-neck t-shirt and navy and white sweatpants are a great go-to getup to keep in your off-duty sartorial collection. Want to play it up with footwear? Complete your look with white canvas low top sneakers. So as you can see, this ensemble is a really smart option, especially for awkward fall weather, when the temperature is starting to drop. A no-brainer ensemble proper for 20-year-old guys who prefer to dress casually.