None/all.
alinguistic hooting/hollering
Icelandic :blob-no-thoughts:
Chinese has the most native speakers. Spanish has the most countries and English is the most common second language. So between the three of them you have a huge chunk of the world population covered.
Not saying there really should be an “official” language but there will need to be a lingua franca because putting two dozen languages on a street sign doesn’t help anyone.
2000 characters gives you a ton of coverage unless you’re working with obscure topics (which you’ll pick up from context anyway). I would also say that speaking is significantly more important that reading, writing, or listening, and if you focus on that as a first objective (but not the only objective of course), everything else will come pretty naturally.
Why would you want an official language?