The type of cat litter for the litter box is critical to the success of litter box training. Your cat will be most interested in the smell and texture of the substrate (litter).
Your concerns may be safety of use, scoopability, disposability, and odor control. The bottom line, of course, is "will your cat use it?" Read the entire article.
For a totally natural and environmental slant on the subject, view this previous post.