I bought a 250yd roll, Kroger brand, and that was a mistake. It was poor quality, fell apart, and left strands in my mouth. It was only a dollar so I threw it out.
A tip to use less floss: Take a piece only about 6-8" long and tie it in a loop (a figure 8 knot is good since an overhand knot probably won't hold). With this a 100 yard spool will last me more than a year.