>>18491977 (OP)Okay first of all that's not a trench coat, it's just an overcoat.
A trenchcoat, as the name implies, was a jacket with a bunch of belts around it, to keep soldiers dry in the trenches, it was often waterproofed and stuff like that.
But anyway, it's all about proportions. How long it is, how tall you are, how wide it is, and how fat you are.
If the coat is too long, it makes you look like a kid in his dads clothes.
If it's too short, it just looks cheap.
If it's too wide/loose/baggy, it makes you look shapeless, it should hug the model to a certain amount.
If it's too tight and can't be buttoned, it makes you look fat, and it makes the coat look cheap.
You absolutely must wear it with formal clothing, that is the key difference between looking good in one vs looking like a neckbeard. Do not wear jeans, do not wear cargo shorts, do not wear boots, do not wear tshirts.
Wear a white or blue collared shirt, wear dress slacks, you can get away without a tie or a suit jacket if you really don't want to wear one.