What's the limit?
I'd like to keep the monster trio and then probably add; Jinbei, as he is a powerful non-df user and helpful in the water; Red Haired Shanks, as he is a emperor and knows how to have a good time; Hancock, as she and Luffy make a cute couple and you need at least one woman; Dragon, since he appears to be a wind or storm logia type and his powers would definitely help navigate; and probably Rayleigh as he a veteran of the seas and is one of the most knowledgeable out there.