You'll get the full experience on 100. You can always take more, but never untake what you've had. My brother had a rough first time because he dropped with someone who was a bit of a warrior.
MDMA is a great drug, but best when used responsibly. I avoid alcohol with it these days too, makes for a much cleaner night and a better morning.
I agree with starting with 100–150mg, and my suggestion for harm reduction is to take 5-HTP for a few days after a trip to restore some of the depleted serotonin. The post-MDMA funk is real.
Also, never redose and never chase the dragon. You will never relive your first MDMA experience, so make it count and enjoy it.
TLDR do it around people who aren't going to mind that you're obviously on MDMA
But of course socialising sober is and feels better, though it does not come as easy.
I must've been pretty clearly high as a kite, but the lesson I learned that night is that people generally are approachable, not that scary and we just want to have a good time. The negative side effects was thinking I had fallen in mad love with a complete stranger, and the extreme dehydration that caused me to drink about 5L of water over as many hours.
I haven't taken MDMA since, I plan to try it again later in my life when I'm content with my place in the world (no more than once a season, as Shulgin recommended), but it was certainly an eye opening experience I will treasure forever. This relaxed and optimistic view of the world and other people has been with me since that very night.
With the correct set and setting, MDMA is something everyone should experience once in their lives.