A black shirt jacket and chinos are the perfect way to introduce some elegance into your casual lineup. If not sure as to what to wear in the footwear department, go with grey suede desert boots. All in all, semi-formal and mature enough for a man in his 20s.
When the situation calls for a casually smart ensemble, go for a black shirt jacket and chinos. A pair of black leather casual boots can integrate effortlessly within a multitude of getups. As you're going from your 20s to your 30s, you probably want to start dressing like a grown man. That's when ensembles like this are a life saver.