One of the best ways to style such a hard-working menswear item as an overcoat is to wear it with a sweater vest. Get a bit experimental on the shoe front and dial down your getup with a pair of grey athletic shoes. This combo shows that heading into your 30s is no reason to avoid casual outfits.
Irrefutable proof that an overcoat and a sweater vest look awesome when you pair them together in an elegant look for a modern dandy. Add a more informal twist to an otherwise mostly dressed-up look by sporting a pair of black leather casual boots. As you're going through your late 20s, you want to start dressing more professionally. In this case, getups like this are a safe option.