you can feed it boiled skinned green peas do not feed it any other human food like BREAD CRUMBS, that will bloat ur fish, hot dogs are okay but is not healthy, just feed it veggies like chopped mini lettuce, cucumber flesh and thats it, those are the only human food that i have succesfully fed to fishes including goldfish.
but the most important thing is the water quality, goldfish die quikly when their water gets dirty, as u know goldfish are ammonia machines and pollute their water very easy especialy if you put it in a small bowl or a container, please use a big rubbermaid box, and make sure ur water is dechlorinated, as the chlorine in tap water kills any fish. when u buy the goldfish food, you should buy the goldfish flakes, as most likely the goldfish u have right now is a baby and did u know that orange common goldfish gets to AT LEAST a foot long? meaning you will need a 55 gallon tank in the FUTURE, but it takes a couple of years for goldfish to grow that size, so you dont need to worry right now just be aware. if you dont have a filter get one as soon as you can. get one that pumps up to 60 gallons the minimum, as you will need that for now wand later, also i would suggest that the container or tank where the goldfish is living is no smaller than 20 gallons, my goldfish survived in my 20 gallon tank for 17 months! then i moved him to a 55 when i had more money