Luffy found out that the price for winning the tournament in the colosseum is the Mera Mera no Mi and decided that he doesn't want the fruit to be eaten by just anybody. Therefore he joins the fighting disguised as Jackie Chun, his first action being beating the shit out of what looks like the biggest gladiator around. Way to go incognito, Luffster!
The other important sub plot is Sanji hooking up with a hot babe who asks him to kill a man for her. Granted, that was random but DAMN! that girl's fine! I'd totally tap that. And I'm a girl, mind you.
Opinions: So apart from me drooling over Violet, the chapter was okay-ish. It's a filler chapter. No need to say much about it.
I found it really cute how Luffy asked Franky if he wanted to eat the Mera Mera no Mi so casually. It seems that Luffy is fine with one of his friends eating it, regardless of who it is. (Brace yourselves, "Who will eat the Mera Mera no Mi?" theories are coming!)