Years ago I read a blog post that I found good: it recommended that advanced dancers ask new dancers (especially one who are there for the first time) within the first hour of the dance.

After that they can focus on partners on their own level.

(Obviously you can't make that mandatory – it's a voluntary thing you decide for yourself)

The newbies are less hesitant when they don't know yet that their dance partner is very good. They have a good time. And when they see their dance partner from earlier do really cool and advanced moves they feel that the scene is welcoming ("such a good dancer actually asked me to dance").