Any tips on how to make my index cards into good tarot card stock?

You guys are giving me great ideas Thanks so much

Amazon.com is so awesome

500 cards? Wow that's a lot XD But if I am really happy with the cards I finish making, perhaps I will make another deck I am doing the usual 78 card deck

Take a foam brush and paint the front and back with decoupage (Mod Podge). It'll adhere the cut-outs to the index cards and make them a bit more rigid. And it's really cheap!