I would say, stick and focus on sports you have knowledge of. If it is one or two, that's really okay than having random bets on sports bets you have less knowledge of, just because you are searching for gambling wins.
You are correct by saying that having multiple sports bets doesn't increase the chance of winning in bets, it is losses instead. A gambler who intends not to lose more than he bargained in gambling should stick to the one they have knowledge on how to analyze the match results.