I'd start off with the Himmelveil TLX sets - Streets and Docks in particular. You will be likely to use them throughout the campaign, so you are buying for the future as well as this particular adventure.
The TLX Hinterland Cliffs and Hinterland Forest sets are also a good place to begin, again, it will likely be useful in the future. Cliffs in particular seem to abound in the first adventure.
You might be able to use the Maiden if The High Seas as a starting point for building the Coaltongue - the shape is right, but the Maiden is definitely a ship of the age of sail, of wooden ships and iron men, while the Coaltongue is ironclad and steam powered.... But it is a start.
Also handy would be The Legend of Skull Cove - cliffs, idols, palisade fortifications, more docks, native huts, some smaller boats, and a few shark fins for moving around on the water.... No longer available from World Works, but can be purchased from Paizo. It may be available again for a short time, when World Works puts up a section for 'retiring' sets.
If you want to keep with the exploration of
then Swampwoods Village would likewise be useful. (Or as a replacement for Skull Cove, if you already have Docks.)
Ditto for Deadly Encounter, a safe bet, since it is
free.

I think that
might be the only place in the setting where the portal
might be appropriate.
The
and the
might best be covered by either Himmelveil Streets or the older Castleworks Ultimate. Neither is quite perfect for the role.
The Auld Grump