Chamomile tea packets (100%): $0.98 a box (about 4 days use): Natural anti-inflamitory, I've used it on a few swollen legs (nothing major, clumsy thing bumped herself on a log) and swollen bug bites, the swelling was down within a few days of use.
Garlic (fresh): About $0.50 a clove: Lots of health benefits, amazing for the immune system.
Paprika: I forget the cost: For the non-showing equestrians, not only is paprika a great color enhancer, it also gives a boost to your immune system.
Apple Cider Vinegar: About $4 a gallon: I swear by it for thrush.
Hmm... pretty sure I have more somewhere in my brain, but those are just the ones that came to mind.