When the situation allows a casual outfit, consider pairing a black turtleneck with black cargo pants. Dark brown leather oxford shoes will bring an added touch of polish to an otherwise everyday getup. Outfit inspo like this will help you stay incredibly fashionable while getting into your 30s.
To don an off-duty ensemble with a modern finish, reach for a black turtleneck and navy jeans. For something more on the classier side to complement this ensemble, add a pair of dark brown leather oxford shoes to this look. As a young gent, you probably want to start dressing maturely. That's when combinations like this are a safe bet.