1. Wearing sandals or flip-flops too much. Even without socks, you can't wear them all the time. If you're getting even slightly dressed up, throw some actual shoes on.
2. Buying sunglasses that don't fit your face. Just because they're expensive doesn't mean they'll look good on you. So either stick with what works, or google what looks best with different face shapes. And if you go to a store, bring someone for feedback.
3. Wearing shorts to events that are more formal. They're the most practical choice when it's hot out, so that's why guys do it. But you can't always get away with shorts. So it's a good idea to invest in at least one pair of lightweight cotton or linen pants.
4. Going sockless without taking any precautions. Wearing loafers or boat shoes without socks is in style right now. But you'll probably end up with blisters the first time you try it. And your feet will start to stink after a while. So either wear no-show ankle socks. Or sprinkle some foot powder in there to soak up the moisture and let them slide a little easier.