Go for a simple yet casually cool choice in a denim jacket and a white and black short sleeve shirt. For something more on the elegant end to complete your getup, complement this look with a pair of brown leather casual boots. Keep this look in mind come warmer weather, and we guarantee you'll save time getting ready on more than one morning. And if we're talking casual dressing ideas for 30-year-old gentlemen, this combo looks nice on almost any gent.