BLACKMOOR
Adventures in Blackmoor [DA1]
City of the Gods [DA3]
Duchy of Ten, The [DA4]
HOLLOW WORLD
HWA1 Nightwail
HWA2 Nightrage
HWA3 Nightstorm
MYSTARA
Atruaghin Clans, The [GAZ14] (*) (CAN $20)
Endless Stair, The [CM8]
Minrothad Guilds, The [GAZ9] (maybe) (rare?)
I'm a fan of the Blackmoor series, so I suggest picking up
DA1 Adventures in Blackmoor and
DA2 Temple of the Frog, especially (I know DA2 wasn't in your list, but it's worth keeping an eye out for).
DA3 City of the Gods is interesting, and has a bit of a connection to DA2, but not enough that you need the earlier module to run this one. The City itself is not well fleshed out so I feel there's a lot of work to be done there, but to be honest I don't really know if I would have liked more detail. You're already getting into some weird stuff there, anyway. I recently grabbed
DA4 Duchy of Ten but haven't had much chance to read it. If you only get one of these, get DA1 -- not for the adventure so much (which is a way to get your PCs from the modern era into the past to have adventures in Blackmoor), but for the nice campaign map and good mini-gazetteer of the Blackmoor world. If you only get two Blackmoor modules, try to find Temple of the Frog. My one complaint about the Temple module is that the maps have some rooms that weren't drawn to the proper scale -- you'll have to correct that by modifying them for play. Still, very entertaining stuff in my experience.
To take advantage of the Hollow World adventures, you'll need the boxed set. The adventures themselves take surface-dwellers on a whirlwind tour of this whole area and they end up seeing some very interesting stuff. The adventures are great from the standpoint that they introduce some new areas and have some of the high-quality maps that the D&D game of that era produced. The adventure itself isn't so hot, though. I found the overall plot to be somewhat (wait for it....)
hollow. Yeah, I went there.....
The
Atruaghin Clans Gazetteer is my least-favorite of the series. While the fold-out map is good, you're looking at an American Indian inspired setting. If that's your cup of tea, then this might be of interest to you, but I felt that it didn't fit the feel of the rest of the world. You also get a passage into the Hollow World campaign setting, but even when I bought this book as a teenager I felt that the connection was more gratuitous than logical. Overall, the setting feels like it was created to help get people into the Hollow World rather than to complete the
Known World regions from the Expert Boxed Set. I wish TSR had focused on the Heldann Freeholds, or the Kingdom of Wendar instead.
CM8 The Endless Stair is written by Ed Greenwood. If you're into 1st edition Forgotten Realms material (and I am, so consider my viewpoint as biased) then you'll find this a fun adventure. It really isn't strongly tied into the Mystara setting, so you could pretty easily throw it into an FR game (or anywhere else you like). Overall, I recommend it if it's a good price.
The Minrothad Guilds gazetteer is a reasonably good pickup if you're interested in lots of guild info, as well as seafaring trade info for the Known World. If I recall correctly, it is matched by the overland trade info that comes from the
GAZ11 Republic of Darokin gazetteer. It doesn't contain the cool ship combat minigame that was introduced with
GAZ4 Kingdom of Ierendi (which disappoints me) but does have some decent info in it. It's not my favorite of the GAZ series, but if you're looking to round out your collection, I'd recommend picking it up before the Atruaghin Clans...... There is a prestige-class-like class introduced in this book -- the Sea Merchant? (can't recall as I'm at work) -- that I think anyone can take and gets some interesting spells. I never played/encountered one in play, and I can't vouch for balance, but it was an interesting early concept of a non-base class that you tack onto your character later.
I hope some of this helps to make some of your decisions a little easier!
