For an outfit that's casually classic and envy-worthy, wear a navy plaid suit and a grey wool turtleneck. And if you wish to effortlessly ramp up your ensemble with a pair of shoes, why not make brown leather loafers your footwear choice? Warmer days call for cooler getups like this one. So if you need style tips on what to wear as you get into your 30s, this ensemble is perfect.