Here are some helpful resources for the campaign.
Jade Regent Player’s Guide Make sure to read this. It’s short, but will be important. It contains tips for character builds for the campaign, an introduction to the major NPCs, and other good stuff. Also, it is free.
This Paizo List contains a list of books that will be helpful, but none of them are strictly necessary to buy.
Maptool Website We will probably be using build 87.