How come the same clothes have a different effect when worn by different people? How can I look more casual?

Maybe your outfits are too busy lol, maybe theres a non-confident feel about you and thats why you dont look casual. People have a sixth sence for this stuff lol. Just try and keep your outfits as basic as possible :) and dont worry so much about what others think about you! theres nothing wrong with looking dressy.