I had a tank a about 5 years ago, and I have just recently re-set it up, The filter is a Whisper® Advanced Power Filter, and the heater is a Top Fin brand heater.
research about tanks and fish types before you buy
1 adult Sunburst tetra, 7 4 month old sunburst tetras, 1 5 week old golden molly, a gold inca snail, 4 neon tetras, 1 male swordtail
fake plants, and one bunch of Gold Ribbon (live plant) and one bunch of Wisteria(live plant)
When you see signs of stress in your fish, you can then take steps to identify the source of that stress and then to resolve it before it becomes a major issue.
If you're looking for a unique way to stock your new tank, give freshwater shrimp a try.
If your fish is suffering, you may want to consider euthanasia as an option to humanely end his pain.