Pair a navy denim shirt with a white and navy horizontal striped crew-neck t-shirt to feel absolutely confident in yourself and look cool and casual. A pair of white canvas low top sneakers is a fail-safe footwear option that's full of personality. When it's one of those gloomy fall days, sometimes only a kick-ass look like this one can brighten it up. If you're not sure how to dress as a 20-year-old, this combination is a winning option.