Are you keeping fancy or regular goldfish? It's tends to be easier to keep fancy goldfish with plants than regular ones. I like to keep my goldfish tank bare bottom so it's easy to clean. I have a bunch of glass crate and barrel candle holders with osmocote + and eco complete in them that I use for plants. My goldfish uprooted the stem plants that I tried, so I don't keep those in the tank anymore. I've had great success with anubias, java fern, buces, swords, banana plants, and crypts. I can't keep moss in the tank either because they eat all of it. Another thing that has helped me is putting rocks around new plants so that the fish have a harder time yanking them out.