How do I read this panel? I have just started reading one piece and came across this panel. I think I know the order panels should be read and I know to go from top right to bottom left within the panels, but I found the one above a little confusing. What order should I read the bubbles and who is talking in each box?
The right order to read these is as you stated:

Top right,
Bottom right,
Left.

I believe Nami is the one doing all the talking, but I get why you'd be confused: the speech bubble on the left has a really short tail, and Luffy is closer to it than Nami is. However, judging by context (the bottom right and left statements seem to follow logically) plus the fact that Luffy doesn't have his mouth open, I would say it's fairly reasonable to assume that Nami is doing all the talking.