I prefer to use multiple herbs in a formula instead of just a few. It seems to have a greater effect this way, this is something I've also learned from other herbalists.
Here's a link to some formulas for specific areas of the body to help you get started. Herbal Formulas
Go down to my post within the link and you'll find a couple of files with those formulas.
Lately I've not even bothered with making tinctures, I've simply been grinding up the herbs and putting them in capsules. I am liking it far more than a tincture, it seems to be more effective as well.