The Rebel G uses standard 35mm film. I don't know what part of
the world you're in, but here in the USA 35mm film is available at
any camera store, as well as many supermarkets and drugstores. Of
course, camera stores will have a better selection, other stores
are limited to color print film.
I usually buy my color print film at a local supermarket, where
it's about $1 per roll of 24 exposures.