I'm assuming the traje is just the gown? Bit difficult to see in that photo. And you just wear black trousers or something underneath? Certainly seems something much "bigger" than anything equivalent we have here.
It's different for women and men.
Women wera a skirt by the knee or 3 fingers bellow it, black tights, around 3 cms black high-heels, white blouse, black tie, black vest and that suit coat.
Men wear trousers and a long suit coat. The rest is simillar to the women's traje.
Finally, everyone wears that black layer. I don't know the correct english name for it, we call it capa and it's very long almost touches the floor and we use it in our back. I think it can be considered the most important part of the "traje".
Sorry, can't explain it better than that.
I'll try to find a better picture.