I’d say 3 people is enough to be enough company but not overwhelming for a party.
Sure, I know it’s a small number.
I don’t get out into huge parties, and doing things in huge crowds does not sound like a perfect party atmosphere. If there’s too many people in a party, how will you have ‘enough fun’ to spread around to everyone? How will you keep the whole group satisfied? How will you focus on seeing and talking to everyone?
All the parties I attended that were noisy, busy, and full of too many people always leaves something to be desired. Usually it’s too hard to talk to someone, or you have to fight across the room to get to the half empty bowl of chips.
If you have only 3 people, you can converse with everyone at the same time, fool around, -whatever, and it’s not a problem. You don’t have to waste time waiting for everyone to show up, or get organized. Three people can just get up and go, and it forces you to try to have a good time. The best parties I’ve gone to are when I’m with three good friends, even just one other person, and we probably had more fun than a whole stadium of party-goers.