i can sell anything

i found myself in an alternate world that is about to experience an apocalypse. this apocalypse is different than the stories. alien merchants could be found in villages and cities. monsters drop coins when they die. food can only be obtained from these merchants. nothing is edible in this world. people can only have one power. how to survive in this apocalyptic world? buy weapons and items from these merchants. my power is not an attack or defensive power. its not even support. but with it i can survive in this world.