Beautiful dress! I've also got a wedding coming up and will be wearing a grey sparkly dress, but mine is a darker gray and doesn't have beading. I'm planning on going with purple suede pointy toe pumps. Partly because they are in my closet, they fit, and I struggle with finding pumps that I can stand in and dance in. But also I think I like the additional & contrasting textural interest of suede with sparkly. Could do a pump in any color that goes with grey.
Angie suggested sparkly tights so I'm debating that. Otherwise, I'll go with simple sheers.
For bag I'm going with a metallic grey clutch. Cream would work great with your dress, to complement the pearl beading. Or bring in color with the clutch, and then keep the pumps neutral - grey or black. What color is your hair?
For jacket/blazer/topper, I haven't decided. Do you have a tuxedo jacket? I think that would totally work.
Jewelry - I'm stuck on that one myself. I'm leaning towards no jewelry, as I haven't been wearing jewelry lately anyway. What will you be doing for that?