Basic Medicinal Herb Garden

What is a good group of general medicinal herbs to get for under $100? I am interested in herbalism, and want to grow my own herbs, but there are so many herbs that do almost the same thing. What is the best combination to grow for general use, that work well together? I need herbs for headaches, stomach upsets and ulcers, fatigue, general soreness, asthma, immune boosting, cough, allergies (dust, dander, pollen), etc, and herbs that help the others work well.

You would be well advised to get Tammi Hartung's book, "Growing 101 Herbs that Heal" (available from Richters). This book covers the medicinal herbs that are practical to grow in the garden. Many medicinal herbs come from extreme environments such as tropical forests, alpine areas, deserts, etc. and they cannot be grown easily in home gardens; so a book like this one is very helpful to help decide which to try.
Some of the herbs to consider are echinacea, St. John's wort, valerian, comfrey, goldenseal, calendula, gotu kola, peppermint, mullein, arnica, and cayenne pepper. Hartung's book covers others that you can grow.