About 5-6 years ago, back before I got way into fish keeping, I got WAY into keeping Hermit Crabs. They were great little compainions, I really enjoyed keeping them. xD
I don't remember a whole ton, and I'm certainly not up to date on the most recent trends in Crabbie-keeping, but I had a fantastic forum I was a part of, very much like this one, with experienced keepers with all sorts of wonderful helpful information. I don't believe I'm aloud to link to it, but if I remember it was called Hermit Crab Paradise. I'd suggest checking it out. ;)
I do recall however that they like groups, the larger the better. I was always told that in the wild they traveled in very large groups and were very social creatures. They're also little escape artists, you'll definitely want a very secure lid......I watched mine climb up the silicone in the tank once and PUSH open the Screen top lid!
I started in a 10 gallon and eventually upgraded to a 20 long, play sand substrate, and a screen-top lid with plexiglass laid over it(though I remember plastic veggie wrap does the same)to help keep in the humidity.
If I had kept with it, I probably would have had to upgrade again even.....I believe most of the serious keepers used 40 breeders-55 gallons.
I also remember I was able to find spare shells and a few other awesome decorations at craft stores for a little cheaper then at Petstores and whatnot.
Sorry I couldn't offer much more help.....its been so long since I had Hermies. xD But good luck, and good for you for doing research! One thing I do remember is that there are a TON of misconceptions about Hermies and proper care for them, a lot like bettas.....ugh, those terrible little Kritter Keepers, the calci-sand, the painted shells....Dx
Anyway.....hope I could help a little bit, and I wish you the best of luck! I'd love to see pictures when you get everything setup. :)