An orange crew-neck t-shirt and black chinos are a pairing that every modern gentleman should have in his wardrobe. Go the extra mile and spice up your outfit by sporting a pair of white athletic shoes. Needless to say, it's easier to work through a hot summertime day in a fresh look such as this one. When it comes to casual style tips for 20-year-old gents, this combo looks nice on almost any gentleman.