Hello~ Thank you for writing the whimsy back into this genre, hehe.
As for HB's books; honestly, you can't go wrong with my overall favourite, The Folk of the Air trilogy as a starting point! You can follow it right up with The Stolen Heir duology, if you're keen on seeing what some of the minor characters have been doing.
Modern Fairytales trilogy follows a changeling protagonist, but the language is kinda outdated, lol (it was released way back in 2002), but the design of the leads are my favourite (Kaye and Roiben make such a beautiful pairing).
The darkest part of the Forest is neat if you're looking for a quick and fun read as it's a standalone.
All of these stories take place in the same universe, but you don't miss on anything if don't read them in their publishing order, apart from some cute little cameos and fun easter eggs :D.
Happy summer break to everyone!