What is coming through on this thread is posters seem to start with a mental picture of what they are or want to be/ would like to be. So there are eg iconic women from the music world, members of the Bloomsbury Set and the Fabian Society, intimidating avant garde artists, high flying lawyers, characters from Jane Austen and Thomas Hardy, members of the Bauhaus group, Goths and Vampires, some Grace Kellys, Katherine and Audrey Hepburns, and Helena Bonham Carters, some family members from Little House on the Prairie, several Amish and Quakers. This isn't cosplay but more a way of grounding a starting point.
Sadly, I'm much more practical and less romantic than that. I have a hard to dress shape - I'm short (5'3") and small (size 6-8), but a pretty definitive hourglass, with a short torso and long legs (for my height, so all relative), so I can't just throw on anything and look good. All the androgynous, hangy, boxy, billowy, drapey gorgeous stuff on this thread and all the current ruffles, puffed sleeves, balloon sleeves, overly long sleeves, giant bell sleeves, long pooling trousers, voluminous midi dresses etc. etc. make me look either like I'm a child who's emptied the dressing up box, or a head floating atop a shapeless mass of clothing. I need to show either wrist, waist or ankle and preferably all three.
So my starting point is will this be flattering and how much alteration will it need- I learned years ago that stuff that's too long doesn't just need hemming for me, it needs to taken up properly from the shoulders. If the waist doesn't hit in the right place, it won't work. Second point, is it worth the money; third, is it vaguely fashionable, which is tied into the second point, because if it's too trendy, it's unlikely to be worth the money.