understanding phono cartridges

so as i'm new to the analog game, i dont fully understand what makes a cartridge a good cartridge. and as such, i would like to understand better, so i can make a good decision when i buy the cart for my jvc a-l31. i dont have a whole lot of money to spend, and as it seems the tonearm on this deck is a low mass guy (i make this assumption based on the fact that its a thinner arm) i know heavier carts are out. so im looking at mm cartridges basically. any insight into what really matters in a cartridge, and suggestions that would work for me would be fantastic and greatly appreciated!
my bad, its the l-a31...
I'm a London Decca fan(moving iron), but this thread really opened my mind up as to what is possible on a modest budget with mm:


well...over 1000 bucks for a cart is a bit much for me..haha by my standard, thats not so much modest as it is high priced...im talking under 200 bucks here. (i got my turntable for 40)
Grado, AT, Ortofon all have great cartridges at around $200.
The thread referenced above is excellent. You are looking for good tracking, good extension (or "frequency response"), good engineering -- i.e. an old model from a reputable manufacturer...
All that, without being too choosy, should set you back ¬130.
Try a Shure M97xe. They're less than a hundred bucks and they have a very nice warm sound. Not the last word in detail but a very satisfying listen.
actually, the shure was one of the ones i was looking at. its 140 on needledoctor.com, but i know ive seen them cheaper elsewhere
yeah, 60 bucks on ebay brand new...but that will work well on a thinner arm like the one on my jvc?
I used an M97 on a Grace 707 arm, which is pretty low mass. Its a good all-rounder for a starter setup. Sounded very nice.
Audio Technica AT-91, at about 20+ to 30 bucks, its almost free. Anyone listened to it before?
I have a M97 that I use on my Technics table with very good results, a fine sounding cart that should make you very happy esp for $60, which I paid on ebay.
Yes I have the AT-91 and I use it when I am checking out older records that have a scratch or 2. It is almost unbelievable considering its price. I just added a new stylus for $15- and it will get you 90% of the music/sound of the M97. Of course being an addict I am more than willing to pay for the last 10%. Isn't this hobby all about paying exponentially for small incremental advances?