As a Tropical Fish person, i will give you a Tropical Fish opinion.
You can use either gravel, (what I use) or sand for the terrain. Fake and or live plants work well. 10 gallons is quite fair for any of the Betta and Poecilidae (Guppy, Endlers, Platy, Molly, Swordtail, etc.) species as the main fish, and Corydoras as bottom feeders.
Fightn' Tips: 1. Using live plants helps you cut back on water changes.
2. Using multiple 10-20 filters helps you cut back on water changes.
The rule of thumb is 1 gallon per 1 inch of fish. But of course if you have bigger goldfish you will need more room. So for larger fish, go 1 gallon per 3 inches of fish.
They can just live in an aquarium with the normal pebbles on the bottom that all fish live in.
No, you need a 10 gallon aquarium. Bettas should not be kept in bowls at all. 2.5 gallons is the minimum.
One gallon is really just too small for any type of fish, but 2.5 gallons or more would be great for a betta fish.
An aquarium, if you want plants, depending on the type you may need substrate, a filter, sand or gravel about 1 pound per gallon, a light between 5000K and 6500K (it does not have to say aquarium), water purifier, water, fish food, a power strip that has at least 4 outlets, an aquarium heater if you are going to have tropical fish. and about 30 minutes to put everything together and add water
Fish tanks can be any size; from 1 gallon bowls to 500 000+ gallon public displays. about an inch from the top should be fine, depending on filter, size of aquarium etc.
To have one fancy goldfish you need to start off with at least a 20 gallon aquarium kit. This kit will come with a filter, filter media, the tank, and likely some decor. You also need to buy a bottle of water conditioner, and some fish food so you can begin cycle your aquarium to prepare it for the fish.
One goldfish requires at minimum a 20 gallon aquarium with a filter, and an air stone would be nice
Freshwater aquatic snails would be the best choice for a tank that small.
In the aquarium were water, weed, sunfish, snails, and a neon fish.
10 gallon if its only 2 inches and a 20 gallon for 4 inches
No you will need to treat the aquarium the fish is in rather than the fish. Ich is a microscopic protozoan that will now be in the environment the fish is in and it will eventually infect (attack) all the inhabitants of the aquarium if not treated.