Well, you could close [i]applications[/i] and then give everyone from this thread four days or a week or something to put a character together - if they haven't got one by then, they almost certainly wouldn't have had one ready for a timely start [i]anyway[/i] even if you were just accepting everyone.

Alternatively, you could put everyone's names into a hat/assign everyone a number and then randomly select a group of your preferred size. Personally I prefer a merit judgement, which is why I initially suggested a decision based on quality/depth/potential of character sheet, but at the same time this [i]is[/i] casual, so maybe requiring high standards of presentation and characterisation isn't the most appropriate. On the other hand, you don't have to make your standards massively high, if you're just determining [i]between applicants[/i]...

Etc. etc.

Point is, there are options, and arguments for and against both - but realistically if you were looking for a group of 6, 14 is probably too much. 7 or 8 might be an acceptable stretch (depending on your preference), but even that many can get things really bogged down if the game runs on a more or less sequential turn order.

Honestly I'm just throwing stuff at the wall here, it's up to you what sticks.

EDIT:
[quote=@Elgappa]
[@Bluetommy]
How about a split then? Make two rps, set in the same setting, but at different place? Kinda like a split-off of a popular series! Both are looking for the Avatar, yet both do so for different reasons! 
[/quote]
This would work too. Or just run two completely separate games concurrently.