I started with blonde hair and dyed it a medium red-brown. It turned black! How can I lighten it wihtout completely drying it out?

If you are trying to go more than three shades lighter or blonde, then you will need to use a bleach to lighten your hair and then deposit the desired color. This is known as a double process. If you use at home box color to lighten your, it will result in a brassy or red/orange look. Please go to the salon and have them do corrective color.