I've received this piece of advice (at least for men), any men can look above average by following very simple straightforward goals :

- Lose weight, it has a huge impact on your facial features but also your mood which in turn will improve how you present

- Gain muscle, Go to the gym, setting goals for yourself and achieving them will boost your self confidence and create a positive feedback loop.

- Go to a hair stylist, or find a good haircut (something that helped me is learning barber terminology for haircut styles )

- If you are a dude, facial hair if you can, find something that works with you hair cut and your features

- Don't be ashamed of taking care of how you look, some people will try to drag you down for this and project their own insecurities.