I was thinking of making multiple fairy costumes based on the elements... lol. But for clothes... Keep your clothing in the color scheme of the element.
For air maybe a skirt that is breezy flowy very light maybe almost see through fabric in a light yellow, or even white.
Fire. A gypsy type skirt, with multiple reds and oranges if you can. You want movement, but not light and flowly.
Water. A lot like air. Blues and greens. You want movement and flow.
Earth... for earth I think pants might be good. Earth is the stable element. Perhaps sort of think "tree" when you make the costume.