The rule of thumb: three (3) square feet of dance floor per dancing guest and 2/3 of the party might be dancing at any one time.
For two hundred (200) guests that would translate to 132 guests dancing at any one time. 132 guests x 3 sq.ft. per guest = 396 sq.ft., translating to a 20' x 20' floor. The closest floor to that would be 21' x 21' which is 49 sections.