I'd first suggest you visit your local hobby store and determine what parts they stock the most, then base part of your decision off of that.
Secondly, I'd suggest researching the different makes and models of buggies out there and determine how you plan to use it. You seem to be rushing into this a little bit and I'd hate for you to get the first available rig then grow frustrated when you can't get it running right.
Yes, these are toys in the technical sense, but they are not like the Wal-Mart RC's that you slap a couple batteries in and go. Nitro rigs, especially, require a lot of patience to set-up and maintain and you'd be better off taking the time to learn about them before getting one. Nitro rigs, in particular, must go through a break-in process that can take a couple hours or more to complete fully, even if they say "Ready to Run."
Trust me, do some searches here and on the web in general on the different makes and models before you diving into a purchase. You'll be happier for it in the long run.