I prefer Titebond premium out door wood glue, it is available at any building supply.
I always like the look of a natural finish, using minwax out door polyurethane. The natural finish allows the joints to show up better, it gives the wood a nice clean look. I use 2 coats and I do sand the wood before I apply the finish. You might consider using deck screws instead of nails it is well worth the time. I have found that wax moths are some what more attracted to white, thats another reason I prefer the natural finish.