When I used to make them years ago, I typically just used Elmer's Rubber Cement. I would roll them a bit with a rolling pin and then allow any excess that squeezes out the sides of the cards to harden and then just rub it off.
I know 3M makes a spray adhesive as well but I never tried it on cards.
You can go crazy and use Dry Mount and other adhesives. I have tried many but honestly I stick with Rubber Cement (as Rick said)any more. It is pretty decent, easy to work with, and easy to find. The quality of the card will only be "slightly" less than what you would get by using fancy glues that are recommended in the Gaff factory.