Tile is inexpensive, but labor intensive. If you have it installed by a professional installer, the labor is likely more expensive than the materials. Laminate flooring is more expensive per square foot than tile, but not by much. It's easy to install; you could probably do it yourself.
Carpeting is the more expensive option, and I would advise you to have it installed. Getting carpet pulled just right is an artform.
If you have existing tile, laminate or hardwood, and just want to cover it up, get large area rugs. Good ones aren't cheap, but there's no installation costs.