The game mainly tries to balance the personalities when your town is first being populated. It may still attempt balance when you get down to 8, but the campsite is pretty much random and not governed by what personalities you have. I have three normals and still get normal campers. Because there are so many ways to get villagers, it's possible to get every single villager, and someone here even had that goal.
Depending on what specific villagers you want, you can probably adopt them from somebody here. It's kind of hard to get the very popular or the very unpopular, because there is a lot of competition for the former and a lot of instant voiding of the latter.