No matter where you go over the course of the day, you'll be stylishly prepared in this laid-back pairing of a long sleeve t-shirt and brown jeans. Complete this look with a pair of derby shoes to easily dial up the fashion factor of any outfit. Keep this look in your head come spring, and rest assured, you'll save a ton of time racking your brain for an ensemble on more than one morning. When it comes to casual outfit ideas for 20-year-old gents, this combo is ideal.