New LotfP fan: what to get?

Hello!

Having ran the Cursed chateau I can say that while it's set in France, there's nothing in the adventure that will suffer, if you place it somewhere else. Just rename the NPCs to fit the new locale.

From the published adventures I think only the Squid, the Cabal and the Old Man and England Upturn'd are wholly depended on the historical context. Better Than Any Man is set during the Thirty year war, which makes for an interesting setting, but the adventure can work with any army. No Salvation For Witches and World of the Lost draw a lot from the historical setting, but with little tweaking both work in another setting without losing that what makes them interesting.

On the other question, where to start depends on where you want to go. I think Vornheim is almost essential kit for any GM. For me it was revelatory. Red and Pleasant Land comes from the same author and mixes whimsical horror, excellent dungeon design and good advice.
Carcosa and Qelong are both interesting yet lethal campaign settings. While Death Frost Doom, Towers Two and Monolith Beyond Space and Time all offer unique horror and weirdness. But they all need a certain mindset to work, especially Towers Two bends the borders of good taste.
If you want more GM tools, Scenic Dunnsmouth offers very interesting way to generate a remote town with a dark secret. The old Referee book's free and gives a good overview on how LotFP is intended to be played.
The core rules are easily the most mundane thing about the brand.

So, atleast download the Referee book and Better than any man. Both are free and high quality.

I think many groups just drop them or reskin them as human classes (Spellblade, Barbarian and Ranger/Scout are the most popular names).
I just made them available and offered no explanations whatsoever. "Foreigners are weird! Some look and talk funny, others have pointy ears or beards etcetera!" I don't really use demihuman NPC's so when a player rolls one they usually make their own explanation on how they fit into the world.

Also, in case you got pdf's and not physical copies, I'll say that Vornheim's really worth to have on the table. The drop tables and everything else just work so much better with the dead tree edition.

The referee book's been due out "soon" for a year or so. I think the last news were that it might be divided into monster book and ref guide.

But last new stuff came early summer so I think Raggi has something coming before end of this year. Broodmother Sky Fortress, Blood in the Chocolate are just few examples of what's coming. So far the production quality has been really good, so I've always felt that I've got my money's worth.
But this being OSR, there's more than plenty of non-LotFP stuff to follow. If you enjoy Vornheim, Maze of the Blue Medusa is a megadungeon by Zak and Patrick Stuart. It's also one of the few dungeons that actually have gameable layout.
Patrick's Deep Carbon Observatory is another excellent adventure that's compatible with LotFP. Fire on the Velvet Horizon on the other hand is a monster book with extra weird monsters. (No stats tho, you have to plan them yourself!)
Yoon Suin -campaign setting gets a lot of praise and people say it would fit well with Qelong.

I'll also recommend the Vacant Ritual Assembly and the Undercroft fanzines. Issues don't cost much, but come with lots of interesting content. If you like haunted mansions, Stygian Garden of Abelia Prem and Hell house beckons are both interesting and good takes on that genre.