It's not fair to ask me who my favorite member of the crew is, Sanji. You haven't even met all of them yet.
The other things I can answer. My role with the Straw Hats is that I'm the archeologist. Luffy's goal is to find the One Piece and I believe that my goal of discovering our world's true history is directly tied to that.
As for what I enjoy, I like to read and listen to music. In Vallo I discovered music from other worlds, the jazz from 190's Earth is especially fun. I like to garden, it helps to focus my mind.