Marry a white long sleeve shirt with navy skinny jeans to put together an interesting and city casual outfit. Throw brown suede chelsea boots in the mix to avoid looking too casual. Casual combos for 20-year-old men aren't actually that hard, as you can see here.
This off-duty pairing of a white long sleeve shirt and navy skinny jeans is a solid bet when you need to look cool but have no extra time. To give your overall ensemble a more sophisticated spin, why not complement this look with a pair of beige suede chelsea boots? A good, less conservative combination for a young gentleman.