There are so many outfits for Miku, and at least a sizable fraction of them stand out :/ If you really need suggestions:
* Cendrillon - it's a ballgown with a feather motif
* Cantarella - I've rarely seen this done very well...
* Himitsu ~Kuro no Chikai~ - This is another pimped-out gown.
* Yuki Miku 2013 - It's a cutesified Shinto style wedding kimono
* Yuki Miku 2014 - magical girl style.
* Haruma's Dress Miku - Looks like party dress.
* Poker Face
* bouquet - Dress with some details, but it's hard to see from the references
* Tokyo 2020 Olympics Miku - yukata-derived with detached sleeves with floral design
* Ikoku no Utahime - Google this: 異国ノ歌姫
* Yukata Miku - They release one of these yearly...
RIP CosRevo, Love Laugh, Sweety Pop, Cocosilver.