Basic chassis is done (see it in RG).
Alchemist gets two items for free - I chose Bag of holding for one, probably wand of secrets of the other (rogue in the party)
I will spend 250gp to get proficiency in stealth
List of items (mostly uncommon, mostly utility stuff ) - in order of priority:
Stone of Good Luck
Pipes of Haunting
Cloak of the Bat
Pearl of Power
In no particular order:
Bag of Tricks (Tan)
Circlet of Blasting
Decanter of Endless Water
Element Gem - Summons Earth Elemental (because - swirfneblin)
Eyes of Minutes Seeing - Advantage on Investigation
Mariners Armor
Ring of Mindshielding
Ring of Swimming or Ring of water walking
Rope of Climbing

I know it's a lot, but it just gives you lot more to play with - once you get to 2000gp, just stop
I would not mind even if you reshuffle "big four" - just give what makes sense, I'll make do.
Short story:
- deep under the dutchy there is svirfneblin civilization of three cities in tight labyrinth of tunnels where they lived and prospered. Until such time as the earthquake collapsed some tunnels, damaged others and opened rifts into their midst. After initial furor an investigators team was created because diviners said it came from above, from the surface.
Equipped with items for communication, trained in stealth (even if they weren't before) three emissaries started the mission...