For relaxed dressing with a modern take, you can rock a navy denim jacket and a grey denim shirt. If you wish to instantly rev up this outfit with a pair of shoes, complete your ensemble with dark brown leather casual boots. So as you can see, this combination is a really savvy idea, especially for in-between weather, when the temps are starting to drop. When it comes to fashion tips for 30-something Millennial gentlemen, this combination is perfect.