MDMA should be an enjoyable experience. So always be safe and reduce your risk by:
Trusting your source and testing your sample.
Use the buddy system! Have someone with you if this is your first time.
Space your usage three months apart.
Visit Roll Safe
MDMA - Determining the recommended dosage based on body weight.
Tolerance to MDMA in Rats Exposed to Single High-Dose Binges.
Reddit users on /r/drugs and /r/mdma