For a look that's super simple but can be manipulated in a myriad of different ways, go for a harrington jacket and a turtleneck. For something more on the sophisticated side to complement your ensemble, add black leather derby shoes to the equation. If you're often worried about dressing maturely, this combination is a goofproof option.
A harrington jacket and a turtleneck paired together are a sartorial dream for men who appreciate casual combinations. Want to tone it down in the footwear department? Complement this look with a pair of black athletic shoes for the day. In your 30s, you probably want to start dressing like an adult. If that's the case, getups like this are a winning option.