MDMA powder, purity and quantity

[Lettish]

My friend is being put off by all the bad pills circulating the country. His last drop wasn't exactly pleasant, and is highly discouraged by pills now.

He would like to obtain some MDMA powder. He wants to say first that he doesn't have a testing kit of any sort. If he asks his friend to get some, how does he know that what he has just obtained is actually MDMA? It could be anything, right? Ket, cocaine, base, etc...

He'd like to know if any information can be shed on how much to consume? He's not sure of all these measurements, weights and mg's yet. He did a search but found little or no information.

He's aware he really needs to invest in a testing kit, but wondered if there was anything to initially look out for. Sorry.