I still have no idea what I'm doing as far as training characters goes, but I'm mostly satisfied with this one.

Style should be mostly neutral, but putting 3d in negative prompt is recommended nonetheless

General activation prompt: GFLSakura, black hair, blunt bangs
Vanilla costume: SakuraBase, SakuraBaseHairFlower, single hair flower, red scarf, green half gloves, black pantyhose, floral print, white kimono, black serafuku, pleated skirt
Tale of the Butterflies dress: SakuraDress, SakuraDressHairFlower, single hair flower, black dress, red accents, layered dress

You should be able to prompt for the various modular dress accessories using corresponding tagswhite stockings, white elbow gloves, etc.