but if you want to get the best results of your bets, you need to determine on what sports you really love to watch and follow. And when you're in the right sports, you can easily make judgment from team to team and with upcoming games. Although no one is perfect with it and unexpected things shall come but in that way, you can increase your possibility to win.
And that is the main difficulty of becoming a successful sports bettor, if you really want to have a chance to become a professional gambler then you have no other option but to watch all the games that you can, and as we know that takes a very long time and only the most dedicated gamblers will invest so much time into that activity, the rest of the gamblers will watch a game or two and nothing more and then they will complain about their bad results.
I don't think you need to do that at all. The internet has all the stats and info you'll need to know to determine which team is bigger chances of winning and which team is the underdog. Of course you'll be more flexible if you know the sport by heart, but anyone can have the same info as someone who does with just a few minute research. The more you try to do that, the more you'll eventually know about the sport you're betting on.