Neons may be small fish, but they really are shoaling fish and will not thrive if kept in a shoal of at least 5-6 neons, to have a shoal of neons though this would be too many for a 2gal tank, as others have mentioned they are also active swimmers and are very sensitive to water quality etc. I wouldn't personally keep them in a tank less than tank of the measurements 14x12x10inches (7 US gals) for these reasons and more, however a 10gallon tank would be better.
The Chinese Algae eater is definately too larger growing fish for a 2gal, they have the potential to grow to 10inches+ (although 6-8inches is more common).
A 2gallon tank is good for a siamese fighting fish/betta and a few small shrimp (like cherry, ghost, amano shrimp etc) and a few larger ornemental snails like giant red ramshorn snails or golden apple snails etc.
With a 5gallon tank, you can be a bit more creative, it would be good for 3-5 small growing livebearers like endlers, guppys, platys etc. You could also have small corys like panda and pygmy corys, small shrimp, fish like oto's, female betta's etc.
A 10gallon has plenty of stocking options. The larger the tank, the more stocking options will be available to you. There are many things to take into consideration when stocking fish, like the max size of the fish, numbers they do best in, activity levels of the fish etc.