The standard potting mix that it is in is just fine as long as you keep it at the right moisture level. That is the key to successful rooting of cuttings. I am going to take a contrary view on rooting hormones. I have never found them to make any significant difference. Once opened, the hormone powders lose their potency quite rapidly so you may not want to reuse previously opened powders. But then, I don't think they make much difference anyway.
To have a nice hanging basket of Goldfish Plants, you will need to pot many, many cuttings together. Single stem cuttings will always be single stems. They do not produce more new stems from the roots nor do the branch out. BTW, this is true for many houseplants.
