A tan horizontal striped crew-neck sweater and black chinos are great menswear must-haves that will integrate brilliantly within your day-to-day casual lineup. Complement this outfit with black leather derby shoes for a truly modern on and off-duty mix. As you're moving from your 20s to your 30s, you want to start dressing like an adult. That's when outfits like this are a surefire option.