I just want to put a thought out there that I haven't really seen yet. People are complaining about the quickness of a new member appearing directly after Franky.
My thoughts: Yeah, no shit. It almost HAS to happen. Luffy doesn't have his full crew yet. I was pleasantly surprised when he didn't collect them all before hitting the first half of the grandline… but the second half? We're picking up pace here... there's some huge shit getting ready to go down with the world powers, and the pace is starting to pick up. With that, Luffy has only a couple of stops left before he hits the second half of the grandline.
Obviously, there's no set rule that he should have his full crew before getting there... and perhaps won't. However, I always thought he should make his official entrance into the big league with a full crew. He's about to go into a sea with four emporers with complete crews. I don't want him to mess around trying to round out his crew... I want him to enter with bonds already forged between a complete crew.
But that's just me and my little thoughts/hopes. Although, frankly, I wouldn't complain if he picked up a half giant or runt giant from the giant island..