I don't know what the "next step" is, but I can make a few suggestions. A book on the art really helps (such as Stop Motion: Craft Skills for Model Animation). There are other books out there, so compare them yourself, I can't say which is best.
For equipment, a camera, tripod, some lights, and stop motion software are the necessities.
-The camera doesn't have to be great, but if you upgrade to a better one camera, look up reviews and any problems it may have with filming stop motion. I use a Canon T2i. Pricey, but I also do photography.
-Get a reliable tripod. Anything that, as long as not bumped into, will keep the camera from falling down will work. I use a tripod, as do a few others.
-Lighting doesn't need to be extravagant. Unless he's really into art and worries about lighting styles, moods, etc. he probably won't need anything more than just a few moveable desk lamps. Don't rely on window light as his shadow might disrupt the scene and the lighting isn't even. 
-Stop motion software is ultimate. Invest in this first if he uses a video editing program to make each picture into a frame. The ones I know off-hand are iStopMotion - for mac only, excellent for beginners; Stop Motion Pro - windows only, no clue, never used it; Dragon Frame (formerly Dragon Stop Motion) - both platforms, more expensive, really good, and I now use it. There are also free stop motion programs that you could easily find on this site or through Google.
-I don't do much editing, but when I needed to paint something out, I use Photoshop Extended, since it has an animation timeline for importing movies, which gives me all the photo editing tools I use in photography for every frame in the video. Time-consuming, but it works. I use Final Cut Pro for cutting and adding sound.

So, in short, after stop motion software, I'd go with a better quality camera, followed by the other little things that make the animation stand out more. But, in truth, practice is really the key - as is a good exposure to stop motion films.

Completely agree with the kingster, it is same like a movie does not works better on the box office if it does not have a good story line.
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Tim Manning