Everyone wants to look "fashionable" in this most fashionable of cities, but with tourists EVERYWHERE pretty much anything goes. Heres some thoughts:
No sweatpants or sweatsuits. No flannel jammy bottoms, rubber flip flops or maxi skirts.
You will need a lightweight jacket. The fashionable of both sexes wear leather moto jackets in black:: some ladies wear trench coats. Some shorty wool coats for the ladies and casual blazers for trendy men. but these are bulky to pack. There are a lot of the Uniglo puffy kind of jackets;I suspect they are tourists. No gloves.
Tennis shoes are everywhere and not in white. The young and teens wear converse and tie up lightweight doc martens in black, and brown. Ankle boots for women are everywhere:some knee high boots in black. Just make sure they are super comfortable..you'll be walking a lot. Some sandals seen as it is getting warmer. Some heels but not towering ones and probably a local.
Teen boys wear converse and sneakers.Young men wear leather loafer type shoes often with a square or somewhat pointy toe. They are more European looking than u.s.
Every women wears a scarf. Some of the hip men do--young and old--but the women all do.
Teen and young girls wear very short black knit skirts with black tights. They also wear denim shorts/short denim cut offs with black tights.
I only saw one woman with a hat. Grandmas will wear wool beanies. Only tourists wear berets.
Older men wear fedoras on occasion:some young men wear the pork pie hat or baseball caps
Pants are narrow or pegged. Did not see any jeggings. Denims are often rolled up about two inches from lower hem.
If you go somewhere fancy, a cotton dress shirt for a man, and a nice day dress for woman. Maybe you'd go dressy for the Opera but not in general.
Oddly we saw blacks, browns and greys predominate the woman's clothes. The younger men have often embraced the hot colored denims...blue, orange, been, red.
Just remember, no one is judging you and have fun!