Symptoms/effects of an illegal drug?

I’m looking for a drug for a character in a comic I am making to be on. Unfortunately (or fortunately, depending on how you look at it), I know little about illegal drugs beyond what I have heard or read. I was wondering if anyone could suggest a street drug that would fit into my story.
I have a rough outline of what I am looking for, though. I don’t want it to be *too* extreme nor too easy. (so not weed or crystal meth)
It also needs to be cheap and easy to get a hold of.
The character would have to be sort of coherent as well.
In the story, the character isn’t addicted or anything, it would just sort of be a casual thing.
so, any suggestions? If you have any, could you describe the typical effects of the drug?