The original purpose of a garter was designed to keep stockings up, so if you were to use a garter, logically you'd wear 2 garters to keep both stockings up on each leg. So does that mean a should wear 1 or 2 wedding garters?
In actual truth, it really is completely up to the bride how many garters she'd like to wear. If you are using garters for their original purpose you might like to have two identical garters, one for each leg, however, if you aren't wearing stockings on your big day, simply wearing one for the tradition is perfectly normal. Most of our brides simply wear just one on which ever leg it feels the most comfortable!