Opt for a brown sweater vest and a crew-neck t-shirt and be prepared to be treated like a maverick in the menswear department. Have some fun with things and complete this outfit with white leather low top sneakers. As the weather is getting warmer, it's time to shed those heavy winter clothes and opt for a look that's lighter, like this one here. Guys who are curious how to rock cool casual dressing in your 30s, you have your answer.