For gardening a small amount of soap and oil mixed with water sprayed on plants will kill the bugs and not harm the plants...use after rain and whenever you see bugs/eggs on plants.
Lavender is one of the most incredible bug deterrents. Heard recently that lavender will deter bedbugs too.
Garlic is incredible too. We would make a strong garlic "tea" and put it in a sprayer to spray for bugs.
Grow some of the herbs in your garden and it gets even cheaper to make these herbal bug deterrents.