OK, from what I heard, Betta fish are really hard to take care of. My friend once tried to have a male and a female as pets.
First off, you have to keep them separate, because the male will try to kill the female (I do not know why).
Then, when they create eggs, the male will try to kill the little fish after they hatch, and there are about 500 eggs at a time. They all hatch at about the same time.
You then have to keep the male and the female and the little fish all in separate containers from each other. Even while they are hatching, the little fish will start fighting each other.
Goldfish, I simply don't know much about them, never had any as a pet. I'm sorry that I can't provide any information about them.