What you need to get really depends on what you want to do.
If your interest is landscapes then Terragen/Bryce/Vue are all good.
If it's the human figure then Daz or Poser.
If its 3D modelling then there are lots of options from Blender (free) to 3DS Max/Maya/XSI (lots of money).

Probably the only essential is a good "photo editing" program i.e. Gimp/Paint Shop Pro/Photoshop.

I'd suggest looking at the galleries here, if there something similar to what you want to do then try the demo for that program, though it's worth remembering that the talent of the artist is as important as the program used in most cases. Edited to add: Some programs (i.e. Terragen) have free versions for non comercial use or are free open source (i.e. Blender). There are also often older (full) versions of programs on magazine cover disks which are a good route into graphic art.

Message edited on: 09/17/2005 16:01