Most "international" server.

Um, yea...

Then it's best to pick an NA server. Honestly, JP players might invite you for an EXP party, or maybe an event if they are really desperate, but these days, for anything that takes teamwork and communication, they aren't really into doing auto-translate. I totally get it. If your character is in an important role and it takes them twice as long to get you to understand what to do...