how to upgrade cards is to do the quest line! do all it says and it'll pop up in the quest menu UPGRADE CARD 4 1500g. or fight a false god. there is said it.
I don't often answer calls of duty...but i think it's pointless to keep up these chains because they are blocking out important comments...and by the way...i'm neutral so don't spam me out.
 "Canabalt"){kind=icon}
 "Elements"){kind=icon}
 "Protector III"){kind=icon}
 "Swords & Sandals III:Multiplae Ultratus"){kind=icon}
 "Swords and Sandals IV: Tavern Quests"){kind=icon}