Help! Suggestions for starter fish because I am struggling!

Hello! I had four livebearers and I just cannot seem to keep them alive. It seemed like one was a bully and two of them were unable to get enough food. One by one they died off. I have live plants but I struggle to do the water changes and I think they is also part of the problem. My 2.5 year old loves the tank so I would like to keep it, however I do not know how to keep these guys alive. Send help! Any suggestions on fish that may require fewer water changes? Or might be even easier than livebearers as I am failing?