What else should I do to help my goldfish?

I just got a goldfish at this carnival. its one of those cheap goldfish that dies in a couple of days (or that's what my friends tell me). BUT I DON'T WANT IT TO DIE IN A COUPLE OF DAYS! I put it in distilled water because I know that tap water is bad for them (unless i use those neutralizers/conditioners). and the next day I bought the goldfish food, neutralizer, bowl and gravel that has bacteria that helps clean the water. I been cleaning/changing the fishy's water every day, feeding it twice a day. I was going to buy a tank, but i don't want to waste money since I don't know if it will live that long. I'm currently leaving it in a quiet place so it won't get stressed too much! what else should I do?