Someone correct me if I'm wrong, but I don't think you need a dechlorinator and stress coat, now that I look at both products. Stress coat is a water conditioner, same as the dechlorinator. Quote from the stress coat description
Works to remove chlorine and chloramines and neutralize heavy metals found in tap water for a healthy aquarium environment
Personally, if money is tight I'd go with the log OR the hide out. Whatever is cheaper in store. You can also look around for clearance items in store.
I'm not sure what you can do about the salt, as a water conditioner will remove chlorine and heavy metals, but as far as I know, not salt? Maybe you could do a 50/50 mix of bottled water and tap water?
EDIT: undergravel filters usually don't have good reviews, I would stay away.
and PLEASE PICK UP A HEATER.