What are good beginner fish in a fresh water aquarium, it is a 10 gallon aquarium.?

I am not sure what I did wrong, with my 10 gal aquarium, we followed the instructions and when we got home today, our gourami fish was dead. I am a beginner at having an aquarium and needing to know what would be the best for this beginner aquarium. I am not sure what I am doing wrong, with this aquarium, as I have put in the AquaSafe per instructions, I have the right amount of rocks, heater and a Whisper Filter for the aquarium. My algae eaters are still alive, as well as our other fish. I'm not sure why, our gourami fish died. Please no harsh or rude answers. Like I said, I'm a beginner for owning my first aquarium.
We had the gourami fish for 3 days, and have had the aquarium for the same amount of days.