Picking undergarments

Don't have an illusion bodice but a sorta low cut one, so I'm getting a new plunge bra, and mainly shapewear to smooth everything out lol

Well my dress has a bulit-in corset so I don't need to wear anything but when I tried it on I had my spanxs on so not sure if I'll be wearing them day of but definitely ask alternations and see what they tell you.

Could you have a built in bra put in when you get alterations?

I have a DDD bust and chose a low cut, backless gown. I'm not sure what I was thinking. I asked about adding cups in alterations, but they truly did nothing for me. Now that my dress fits properly, it really kind of holds the girls up on its own. I found a bra called Misses Kisses yesterday and decided to order it. It's backless, frontless, and strapless. My wedding is this Saturday and I've fully planned to just go bra-less, but if this works to give me some more lift, I'll be thrilled. If your dress isn't low cut in the front, I would look into just taping them.