Like it or not, audiences expect belly dancers to have long hair.
If your real hair is cropped short, be cautious about adding a false ponytail. Ponytails bounce as you move - if you're dancing close to your audience, it'll be very obvious that it's not your hair! Your hair needs to be just long enough to pull back and up under the mesh cap of the ponytail, if it's going to look convincing.
A good alternative for shorter hair is a half wig.
Half Wigs on eBay