If you're on the lookout for a relaxed casual yet on-trend look, go for a dark brown cardigan and a white crew-neck t-shirt. Navy and white canvas low top sneakers are a stylish addition for this outfit. When spring is here, you'll love this getup as your favorite for unpredictable spring weather. And if we're talking casual style for 20-year-old guys, this combination is a good look on almost any gentleman.