This is gonna be totally different from person to person, however, I think it's safe to say that stimulants in general are of the most pro-social drugs available to us. I would say, given the entirety of the world's population, most people are going to get these desired pro-social effects from stimulants like Amphetamine or Cocaine.
For someone who is unfamiliar with drugs, Cocaine is much easier to "mess up" in regard to dosing correctly. Delusions of Sobriety, as they have come to be called, typically apply both ways... a person on stimulants is just as likely to not know how fast they are talking/moving as a person on Opioids feels they are having a conversation when they're falling asleep for minutes at a time between sentences.
If you do too much Cocaine, it can be dreadfully obvious; you'll be grinding teeth, licking lips, adjusting your sitting position and rambling without allowing others to speak if you overdo. For this reason, I feel grabbing an Amphetamine pill/capsule is probably the best place to start. There are oodles of different formulations, if you have questions in this regard, we can help you navigate what is/isn't what you're after.
In closing, I think lots of different drugs can make social situations "easier". For instance, Opioids kill my social anxiety instincts (I don't have social anxiety more than any other person, I feel) in tough situations, but I also might tear someone's head off for talking about the weather for too long. Benzodiazepines can grease the wheels of socializing just like their chemical-relative Alcohol. However, they can also make a person seem numb or uninterested. These drugs make these situations "easier" but they don't actually make you more charming or smoother.
Stimulants will have you in 5 different conversations about different subjects simultaneously. For instance, if you're girlfriend's Mom is really into arts and crafts and she's showing you her work, Amphetamines can help you appear genuinely interested, allowing you to formulate questions and responses that make people feel like you're truly engaged. The general boost in energy aids in this, as people will assume that it's just hanging out that has you looking so excited.
But yea, it's different for every person. My recommendation, a couple of Amphetamine tablets. See how that goes and go from there.
