I've recently started making my own herbal tinctures and one that I keep on hand always is Echinacea.
Echinacea is one of the best medicinal tinctures used for a variety of ailments. It helps build the immune system, therefore fighting off infections. It's also wonderful to use externally on many skin conditions (eczema, acne, burns, insect bites, wound healer).
I've also used it for toothaches and sore gums with amazing results! It fights the infection from an abscess, helps heal mouth sores, oh the list goes on...
Echinacea is very easy to grow, so why not get yourself a nice established plant and grow at home!