Consider teaming a navy gilet with a sweatshirt to achieve an interesting and modern-looking off-duty ensemble. Why not take a classic approach with footwear and complete your outfit with a pair of brown leather casual boots? If you're in your 30s, take inspiration from looks like this to take a more mature approach to your style.
If you're looking to take your casual game to a new height, reach for a navy gilet and a sweatshirt. To inject a dose of stylish nonchalance into your ensemble, introduce a pair of navy and white canvas low top sneakers to this look. This combo is most probably what you've been looking for as a 30-something Millennial guy.