What is the best card stock to use for making scrapbook pages?

I am not real familiar with scrapbook terms, so bare with me. I noticed there are different weights of cardstock paper. Which one should I use for the backside of the background paper, so that the page is not flimsy? I purchased some Die Cuts with a View Card Stock from Joann's, but it just does not seem thick enough. Then I thought maybe this is how thick the card stock should be I do not want it to be as stiff as board, because I still have to keep in mind this has be able to fit into a page protector. I have noticed if the pages are too stiff it is a pain in the to make them slide into the page protector. Can someone recommend some card stock to me and where to get it?