Here is one simple format that is easy to understand and to grade that I have played before
$20 bankroll for Derby Day that has to be bet on at least 5 different races... you can allocate money however you want so long as it is on
AT LEAST 5 different races.
$2 Win , Place or Show bets or $1/$2 exacta are the only bets allowed
Biggest bankroll at end of day wins......Must spend all your money, any unspent money is lost