Otherwise single bets is more easier and possible to win, the probability of winning single bet is very high than that of multiple bet as parlay.
Yogee is right, Paroli and Parlay are two different things.
Paroli strategy is when you double your bet after every win, after 3 wins you return to your initial stake, or after every loss. You can read more about Paroli here: Popular Strategies.
Parlay bets are made up of two or more wagers. They are a way of combining individual bets into one.
I like to chase goals... so my parlays are usually about goals, over or under, and both teams to score or not. I don't watch so much my final multi, I am rather focused on finding the right games, so if I think there will be more goals I will include that game whatever the odds may be.