How do I understand Data Stores quicker?

I'm a bit rusty with Data Stores as I have tried it on two projects, but they have failed. I would always end up with data corruption which I always mess up with player reference. I seem to be fine with saving and loading, but when it comes to giving the player more money, I end up giving the rest players money. How can I better my understanding in Data Stores? I'm willing to practice everyday, but I don't know where to exactly start.

My issue is with Remote Events, when I fire them from client to server meaning that I would just end up giving the rest players money. I had a helpful person explain it to me, but forums are down and I can't refer back to it.