Here's a thought. Just paper bet, not real bets, every Under in whatever league or all the leagues. Track the results. Pay attention to the lines and teams, etc, and watch what happens. Over time, you may notice factors or results that will lead you into potential plays. Just one example is the market getting over sold or over bought when recent performance emboldens or lines up with season to date performance for certain teams.
Anyway, track and pay attention, it just might lead you into what some bettors call "spot" plays. This starts your journey into taking more likely or more confident plays and not bet every game. You may have good streaks every game, but in the end the vigorish will eat you up. Eventually you'll learn how to compare your own work to the market and hopefully how to only seek those better plays.
Simple systems to win a little cash each week come and go. They enter and exit through streaks. Even if you have the ability to jump from one hot "system" to the next, it's value is still limited.
Simple systems to win cash each week are also dangerous because of the pitfalls of money management; especially in the face of some success. For some bettors, winning some bets become the worst things that ever happened to them.
That said, simple systems to win cash each week don't exist. They become less simple and the win rate is not realistic. Even one bet a week will have it's streaks, and we've seen some pretty good ones.
Good Luck.