There's a few things to explain about the system. First, the feedback system is pretty poor right now. If you're looking for a notification that someone you reported was punished, you will only receive one if your report was the very last one that triggered the punishment. If you report someone and they get punished after a future game, then you will not receive the notification. If you don't receive a notification, it doesn't necessarily mean that your report is worthless and didn't do anything. If you encounter a toxic player, it is definitely good to report them, as your report will help getting them punished if they continue that behavior.
Now, what do I mean "if they continue that behavior?". Well, with the current system in place, it generally takes a consistent pattern of toxic behavior before someone gets punished. Riot understands that we are human and we can have bad days from time to time, so they do take that into account. If someone has a long history of neutral or positive behavior and then slips up and has a single toxic game, they more than likely won't see any punishment. This doesn't mean that their behavior was acceptable, because it certainly isn't, and if they continue that behavior, then they will be punished, and your report definitely helps in that process.
I person reporting a player doesn't help because we need more then one other person in that game to report them too
Next is this. Despite what seems to believe popular belief, multiple reports in a single game don't really matter. The system doesn't look at the total number of reports a player receives in a single game, it looks at the % of games that player has been reported in, and it only takes a single report to flag a game. Any additional reports doesn't make the system look any harder or faster for unacceptable behavior. This essentially means that 1 report and 9 reports are treated the same, as it is still one reported game. Riot made reports work this way specifically so that larger premade groups don't have any extra power over solo players when it comes to reporting, and so that solo players can still have their voices heard in such situations.