Not quite sure of your intentions to purposefully buy components separately. You certainly would be better off buying a kit to build. That would save you a lot of money.
In another forum, somebody asked the same questions. I responded with my thoughts, and today the post is no longer there. Meh.
I would recommend picking out a truggy that catches your eye; go to that manufacturer's website, and download the manual for that truggy. The manual will give you all the info you need to put together a kit. Part numbers will be in there, and from that, you can research the cost of each individual piece.