I personally do not believe in karma. A lot of people do, and I have nothing against it. I just can't fathom it being a real thing.
In my personal experience, it doesn't matter if you do good or bad. Good things happen to really bad people, and bad things happen to really good people. In my opinion, if karma was real, the world would be a lot more balanced. I honestly felt better once I stopped believing in karma, cause every time something bad happened to me, I thought it was something I had done. And yet every time I did any good, nothing changed.
I feel better just knowing the universe is incredibly unfair, and there's no real out worldly system that judges you on what kind of person you are. I am a good person because I want to be. I want to help my fellow man because I know how hard it can be. I have struggled my whole life, but if I had the money to spare I would carry cash, and sometimes buy water bottles, just to give to the homeless around the city I use to live in. I am no longer in that place, and I have struggled for over a year now due to disabilities. But I'm sure I'll make it through somehow.
Karma is just a philosophy I can't personally follow. But if it's something that drives you forward, to be a good person, then hell, keep at it, friend.