If you are making a rectangular 9 ft. tablecloth, you will probably need a little more than 9 ft. of fabric to allow for turning under and finishing your two ends. I would suggest 3 yards (9 ft.)...
It depends on several factors:
1. The style of the dress - obviously a short, sleeveless sun dress won't need nearly as much fabric as a full length, evening gown.
2. The size of the dress - are we...