Yeah, I try to look for cheap frames, too.  I 
prefer metallic to wood, though, and they're 
often less expensive.  Just make sure, when 
buying a cheap frame, that it's deep enough to 
hold the cel and all the other stuff.  At least 
an inch deep would be good.  I got a $7 frame at 
Target once and coulnd't squeeze everything in :#

I don't use mounting strips, though, I got a roll 
of acid-free artist's tape for $4 at an art 
supply store, it looks kind of like masking tape 
but thinner and not as sticky, and it works 
fine.  I order 11x14 pieces of conservation glass 
for the same store, they cost me $12-13 apiece.  
total cost of framing a cel comes to about $20-25.

As for mattes, I knew that I'd have to frame a 
lot of cels, so I just bought a matte cutter (you 
can get one for about $30) and several huge 
sheets of acid free matting in different colors.  
The sheets were only a few dollars each, and it's 
cheaper in the long run than trying to pick out 
pre-cut acid-free mattes that match your cel.  
But it's only worth it if you plan to frame a 
bunch, and you have sufficient manual dexterity 
to cut your mattes straight.  ^_^

Here's a pic of one of my framed cels where I cut 
the mattes badly -- I keep meaning to replace it 
and being lazy.