I'm 28DD. I wear sports bras a lot of the time, so it's a quest to find ones that work. I love the look of them layered under tanks, but so many of those - like Sweaty Betty etc - start at a 32 back.
On a 28 band a DD is fairly small, and anything like the crop-top styles flatten my chest completely.
The best I've found is an underwired Freya Active moulded one. It's £38 and I'm wondering if I can do better... any padding/underwired/general boosting is welcome.