This smart casual combo of a waistcoat and a white and blue crew-neck t-shirt can go in different directions depending on the way you style it out. If you wish to immediately play down this getup with one single piece, why not complete your ensemble with black suede desert boots? As the weather starts to cool down, you'll discover that a look like this is ideal for this time. This combination shows that as a 20-year-old gent, you have a wide array of dressing options.