Some signs may be more inclined towards magicak work, but you in no way have to be a particular sign to practice magic. In fact it has nothing to do with your practice of elemental magic either. We are all made up of the four physical elements, empowered and given life by the fifth element of spirit. If you want to be successful at magic you have to be comfortable with all four.
The zodiac does give you an idea of your strengths, the influences that are effecting you and the ways you can improve.