Usopp > Zoro > Luffy = Franky = Nami > Brooke
dunnos: Robin, Sanji & Chopper
Yeah, sounds about right.
Ussop wants to become a brave warrior of the seas, and he´s imo the one currently closest to the achievement of his dream. He did some pretty couragous stuff, especially since Sogeking appeared.
Zoro will get his dream along the way, but very likely before the majority of the others. It "only" involves a fight with Mihawk.
Sanji will get his dream before they reach Raftel as well, I think. All Blue is said to be on the GL, that means they should reach it before reaching the end of the GL (Raftel).
Luffy wants to become the pirate king. That involves reaching Raftel. Same goes for Franky (sailing on his own boat around the world: a ship that reaches Raftel can reach every point on the planet). I´d put Robin in here as well, I guess learning about the blank century will be a major point in becoming pirate king.
Brooke will only be able to fulfill his dream AFTER reaching Raftel as he has to go further, back to LaBoon.
I guess both Nami and Chopper won´t fulfill their dreams during the course of the manga. Nami did not yet explore the other 3 Blues, and Chopper will have to research more diseases before he could make a universal remedy.
So I´d say:
Ussop > Sanji > Zoro > Franky/Robin/Luffy > Brooke > Nami/Chopper