The secret to winning sports bets is finding value and picking winners. There is absolutely zero correlation between the complexity of a bet and how likely you are to win. In fact, you could say that there is a negative correlation because a lot of bettors don’t fully understand the complex bets they are making, meaning they are more likely to make mistakes and incorrectly assess value.
In this example the Jets are listed as four-point favorites (-4) over the Bills and the 49ers are three-point underdogs (+3) against the Seahawks. So, if you bet $110 on the favored Jets, they must defeat the Bills by more than four points in order to win $100. If you bet $110 on the underdog 49ers you will win $100 if they win outright or lose by less than the three-point spread. If the final score happens to end up exactly on the number it's a tie, or 'push,' and you get your money back.
Let’s say you decide to bet $100 on the Packers to win by more 7 points and the final score is Packers 30, Seahawks 21. The Packers have won by 9 points, meaning they’ve covered the spread, and you’ve won the bet. The -110 means that your $100 bet will win you a total of $190. That total includes your original bet amount, so your total profit is $90.