Poster: Winston
For starting, especially if you're not sure yet if dj-ing is your thing, the C.313 is an excellent choice. You can discover that although music is your passion, that dj-ing is not your thing. Than it would be a waste of money to spent so much more money on the CDJ-800.
The C.313 with its 4 sampler/loops banks can keep you busy for a long time. Please don't forget that a mixer is also a piece of equipment that takes time to master.
If you're get really into dj-ing you can upgrade your booth. The CDJ-800 is really a player for pro's and advanced bedroomDJ's, which like to use scratch and beatjuggling techniques during their sets.