For a casual and cool ensemble, wear a navy plaid long sleeve shirt with charcoal jeans — these two items go really great together. Look at how well this ensemble goes with white and black leather low top sneakers. This one is a savvy idea if you're on the lookout for a killer getup that will take you from summer to fall. Wondering how to master casual dressing as you drift through your 20s? This combo is a great example.