Short answer, no. A 10g is not sufficient even for one
Goldfish, much less more. Depending upon the species,
Goldfish can get large and they need space and they produce a lot of waste and impact the water quality--all reasons why they need room to be healthy. And I would not mix tropicals with
Goldfish.
As for feeding
Neon Tetra, I would buy some quality tropical fish foods. Omega One, Hikari, New Life Spectrum are said to be good brands, and each of these make several types of food, and variety is the spice of life for fish as much as for humans.
And, welcome to Tropical Fish Keeping forum.
Byron.