A waistcoat looks especially classy when teamed with a black shirt. Outfits like this have a refined air that befit 30-year-old guys very well.
Black Shirt with Waistcoat Dressy Chill Weather Outfits In Their 30s
Make a waistcoat and a black shirt your outfit choice if you're going for a proper, fashionable look. As you pass the big 3-0, you probably want to start dressing in a more refined manner. That's when inspiration like this is very useful.