Undergarments???

It all depends on what you're comfortable with! I'm wearing spanx because my tummy isn't where I'd want it to be and I want that little extra help.

I had a fit and flare dress. I wore panties, no bra, spanx, and a hoop skirt. I wore it all at my
fitting in addition to my shoes.
I decided last minute I wanted a hoop skirt, I ordered it 3 days before my fitting yay Amazon prime!! And I wanted the spanx to help smooth my tummy.

View Quoted Comment Thanks Cassidy! Amazon Prime is the best!

Comfort is key!

It’s all about comfort and what works with your dress, I thought about wearing a girdle with mine but the looking as my pics the back is too low, I’m Gonna wear a high waisted seamless nude panty just because I have tattoos on my waist and there are a couple see through spots on the dress near them and I don’t want them peeking out. I’m also gonna have an little extra bit of padding put in my top because I can’t wear a bra and it’s a sweetheart. Which my FH was adamant I get lol I used to be heavier and my boobs have deflated a bit so I want them to look perky and fit into the cups better.

Wear to your fitting what you're planning on wearing under your dress.
Are you having cups sewn into your dress? Are you going to be wearing spanx? Etc. At the very most remember you'll be wearing it all day on the day of your wedding and you want to be comfortable!

Tbh I went into my fitting in panties & a strapless bra, I had planned on wearing my spanx but couldn’t find it lol but as soon as I went to the dress room they brought me a slip & a strapless corset so it didn’t really matter.! That was at David’s bridal, maybe call the place you plan on shopping at & ask their opinion

I recently just purchased my undergarments from this brand called The Bridal Bra™ on Instagram, I have yet to receive it in the mail but I think it's really reliable for any open-back dresses. I'll attach some pictures of it below so you could have a better idea of what it would look like!❣

P.S. they come in white, nude, and black. I believe those are the only color options they give you.