TK nailed it.  I'm in the same boat as you (new 
collector, not too picky but looking for decent 
shots) and prices really are all over the place.  
The guaranteed expensive cels are like he said: 
Achika and OVA human Ryo-Ohki.  The rest you just 
need to keep your eyes peeled and you have a shot 
at getting good cels for decent ($25-50) prices.

THE RANT:
I just got back from a trip and did a little 
Tenchi search.  I won't mention specifics, but a 
certain auction site has finally gone CRAZY with 
Tenchi cel prices.  Dealers that were once 
reasonable are now asking $500-800 for single 
cels!  A couple might be worth it, but the bulk of 
them ARE NOT!!!  I guess people have been snapping 
up cels so fast that they have decided to put 
ridiculous @%&$)#-ing prices on them just to see 
if anyone will bite.  If we do......god help us 
all.  We'll be paying $300 for Pretty Sammy cels 
soon.

Sorry, but this really ticked me off.  I hope 
these darn cels sit and rot at these prices (but I 
have a feeling they won't!).

JP