To pull together a relaxed look with an edgy take, pair a black and white plaid long sleeve shirt with sweatpants. Have some fun with things and add a pair of athletic shoes to this outfit. As you can see here, as a 30-something gent, you have a wide range of outfit options.
This combo of a black windbreaker and sweatpants is the ultimate off-duty outfit for any guy. You could perhaps get a little creative with shoes and dial down this getup by wearing a pair of athletic shoes. This combo proves that reaching your 30s is no reason to stop dressing casually.