Welcome to Bluelight!
Be very wary of RC's. I would never use MDPV or 4-mmc at all.
I have used and loved MDA though, which is supposed to be more neurotoxic than MDMA, which is supposed to be more neurotoxic than methamphetamine, which is supposed to be more neurotoxic than regular d-amphetamine.
It's also important to weigh the balance between using a drug once, like my IV MDA experience, and then becoming a methamphetamine addict from one use turning into 1,000 more.
The 1,001 methamphetamine uses is likely to be more damaging than just one heavy IV dosage of MDA. (I'm not trying to encourage you to try IVing MDA though, it's way too intense for most people who would enjoy tripping on a mild dosage of LSD).
The reason I say I would never use MDPV or 4-mmc is because they aren't psychedelics, they are totally just stimulants with horrible side effects. If you are looking for just a stimulant, I would choose d-amphetamine.
