I received a BCD, what can I do about my discharge?

PFC Robert Cummings , What part of smoking dope is against the Law and against Military Regulations did you not understand?
I read what you wrote and the replies you have received from the Officers and Noncoms that took time to reply. You have to admit it is a bit ugly. Remember the Board of Correction of Military Records, the board that will consider your request is made up of people like us... Career Military Leaders that have served honorably and by the regulations. So if you are going to submit this, you need to come up with a better story than "It was the fault of the Marine Corps because they took too long and I got bored."
That is the fact and is like the little kid that smashed all his parents stuff and then blames his mommy because she was not home to stop him and he got bored.
I am being specifically hard in this reply, showing no mercy because the board is going to do that as well, you need to be ready for that.
By the way, in the history of the Board of Correction of Military Records, I can not find one example of a characterization of Discharge that was upgraded.
You used drugs while on active duty, you got caught and you got your Big Chicken Dinner, which was I believe well deserved.

You can hope and pray, but you deserve no better than a bad conduct discharge

Yea, you can hope on a wish and a prayer. Don't expect an upgrade, though. A BCD is given at a Court Martial and is sometimes followed by prison time. If the courts found you guilty, and you were given the BCD via the jury and judge, then the evidence was there to convict you.