Halloween // How can I create a librarian-inspired costume using normal clothes?

I want to put together a librarian/secretary-inspired costume for my girlfriend, but I'd rather create the look myself using normal clothes instead of buying a pre-made costume.

I'm going for something cute, feminine, playful and a little cheeky, rather than a very obvious or tacky Halloween costume. I'm thinking about pieces like a fitted white blouse, short pleated skirt, vest/cardigan, tights or thigh-high socks, and glasses, but I'm completely open to other ideas.

I'd especially love suggestions for specific pieces, styling tricks, accessories, or ways to make the outfit feel more fun and character-like while keeping the librarian/academic theme.

I'm also trying to keep it affordable and I'm in Finland, so if anyone knows good Finnish stores, second-hand shops, or inexpensive online stores that ship to Finland, I'd really appreciate those recommendations!

I'm happy with DIY ideas, styling advice, or suggestions for affordable pieces I can buy.