Luffy at the end of chapter 1 according to the Viz says this:
"First things first. I've got to get a crew! I think about ten men should do." Then what does Luffy do next? He goes to Shells Town and recruits Zoro (aka The First). Continuing onward skipping a few, he recruits Sanji (aka The Fourth). Skipping a few arcs, he recruits Brook (The Eighth) then Jinbe (the Ninth). Well, is Luffy The Tenth? No. So its Yamato? Carrot? Caribou? Luffy is not the first its Zoro. I hope this makes sense I dont want to argue with a weetodd for a month.