Yes, as the previous commentor just said, the translation is getting quite long because of the case you need here. Yes, I don't see a shorter way, than "Мне нужно общаться с большим количеством людей." (I need to communicate to more people) or "Я хочу поговорить с большим количеством людей." (I want to talk to more people, note that there's only one "л" in "количество"). "Говорить", "общаться" requires a preposition "с", and you need an Instrumental here, and you have a preposition, so you can't just use "больше".
But if you want to say "I want to see more people" you can just say "Я хочу увидеть больше людей". This is Genitive. "I want to get to know more people" - Я хочу узнать больше людей.