Mine wouldn't work with a sash because of the part under the bust. I really like sashes but going without saved me money! Plus I'm afraid that sashes are maybe a trend that I'll look back on in 20 years and go "what was I thinking??" but I'm pretty sure no matter what we'll all end up looking back at our wedding dress in 20 years thinking that. Trends change so quickly!
No sash. I have another dress for the first look that the consultant tried to talk me into a sash to go with it. It has a floral detail that dips down to the waist. Nope. They are only as necessary as you think they are. Good luck!
I personally am not a fan of sashes either, but I think some brides look great with them. Here is my extremely blingy dress! My Thai dress does have a traditional gold belt, but my Vietnamese one does not have a belt either.