He is so intent on accumulating money he does not want to lose any of the money he has, so he bets small amounts on horses when he is unsure of the winner and large amounts when he is sure of the winner.
A wager is either something deposited as a bet, or something on which bets are laid.
Not that I've ever heard. All bets are not winners - most bets lose the money.
So really silly people can place bets on horses
Punter
They are the people that take your bets at a race track (horses or dogs).
Place bets are in a separate pool from win bets so there is no fixed payout for an even-money favorite.
gambler
Trifecta bets are permutations, not combinations, and there are 6840 of them.
Betfair is a gambling service that allows players to bet on sports games from their homes. It is possible to make money by winning bets using the service.
That is called a bookie or bookmaker.
A bookie