4chan

I hosted a NY party once. I told a bunch of people at work, and random folks I met briefly. Told my neighbors. Said people can bring others. It was a huge turn out of like 15-25 people. The extroverts tend to go to 2-3 parties and bounce around. The introverts tend to go out of social pressure.

Being a host isn't my thing. But NY parties is definitely the easiest party to create and get people to come.

Also assuming you don't live in a cabin in the woods. And you promise food and drinks.