Drug Addiction?

im writing a story about a girl dealing with drug addiction….i want the facts straight, i need infor on
how much is a single dosage (XTC, meth, etc..)
stuff like how longa single dosage usually lasts…how often the drug would be taken
how much it might cost
and what withdrawal symptoms would be
how long between the last dosage and stopping would withdrawal start?
pretty much everything id need to know writing from the POV of a drug addicted girl