Go for a pared down yet casual and cool outfit by pairing a navy sweatshirt and a crew-neck t-shirt. Bring an elegant twist to an otherwise mostly dressed-down look by finishing off with black leather derby shoes. This getup is a never-failing option if you're on a mission for a great, summer-friendly getup. As a gent in his thirties, you probably want to start dressing like an adult. If that's the case, looks like this are a safe option.