You need to know a lot about sports and even then the upsets that seem like sure bets happen quite often.
I'd rather have a go at poker. Less luck involved, but it requires a lot of time and patience.
Really there are people who voluntarily want someone to give their money by playing them in gambling. In general, I think that gambling is a game for experienced people in this matter. They play with each other and this is their lifestyle. A simple user there is better not to climb.