A white long sleeve shirt and olive jeans married together are the ideal ensemble for those who love casual outfits. Complete this ensemble with a pair of white leather low top sneakers and ta-da: this ensemble is complete. Keep this outfit in your front hall closet come warmer weather, and we promise you'll save a lot of time getting dressed on more than one morning. And if we're talking casual dressing ideas for 20-year-old gents, this outfit looks good on almost any gentleman.