In general, to win. Most betting in my circles is done against the entire NCAA tournament. 32 games in the first bracket (1pt ea), 16 in the second (2pts ea), 8 in the third (4points ea) ....blabla
The number of participants set the payouts. Its usually 60% for 1st place, 30% for second and 10% for third.
The longer Kansas stays alive, the more points I get... etc, etc.