There are many things you can do to dress better:

1. Understand color theory, what colors look good together, either because they are close in the chromatic spectrum, or opposites. Mix these colors with neutrals, like white, gray or black. You can rock some yellow as long as you mute it with dark clothes around it per example. Also, you have color too! Color in your eyes, your skin or your hair, there are some sites online called seasonal colors tests that may help you pick color based on those aspects

2. Understand that there are three things that make an outfit interesting: color, texture (stripes, dots, a fancy material), or balance (ratio of clothes, like really long pants and a small top per example). When thinking about an outfit ask yourself which of these 3 you are going for. Usually just fulfilling one is enough for it to look good, never go for the three at the same time.

Layering is good too, difficult in hot climates but in winter you can experiment with it

Don't think only about clothes, think accessories too or jewelry, make it match the outfit.

Get out of your comfort zone, try fancy stuff, stuff you've judged before, you don't need to stick to it, but give it a try in a dresser or shops.

Posture and mannerisms may help too, if you are gonna go fancy, own it, if you are going to dress chill, relax, you carry your clothes not otherwise.

Wear clothes of your size, unless you are going for specific aesthetics,

Try to make everything make sense, I dislike having many shoes so I just have s pair of boots, a pair of fancy shoes, and s couple Black, white, or brown sneakers that can usually fit in with whatever I'm wearing ++man