No you can not keep tetras with them. They need different temperatures and your goldfish will grow and eat them. 1 inch goldfish are practically infants! Goldfish grow fast if healthy. They won't stay small for long.
As said above 5 fancy goldfish need a 60g tank and 600g/hour worth of filtration. They also need large weekly water changes (1-2 50% per week on a correctly stocked tank). They are messy fish. They produce A LOT of waste. I keep tropicals and fancy goldfish and I can tell you the goldfish require more work to keep the water clean and the fish healthy.
Please don't over stock your tank. It can lead to stunting and disease if the waters not kept pristine which is next to impossible in an overstocked goldfish tank.