Hi! Air is the most compatible with air being that they're one in the same energy wise. Same goes for fire and fire, Earth and Earth, etc.
It's dependent on the rest of your chart. The houses, signs, aspects. They all work together.
Just generalizing on sign alone, Taurus and Aquarius are no bueno. Too fixed. Earth and air square so you'll have a clash of energy there.
Libra and Taurus are soooo different aside from being ruled by the same planet obvi. I forget that Taurus is even ruled by Venus.