Ok, I bought myself a PDF of the original Tomb of Horrors, so let's take a look at what you'd need for that.
SPOILERS AHOY FOR ORIGINAL S1 TOMB OF HORRORS!
Overall, the most important ones you'll need are Dungeon Depths for atmosphere and trap sounds, Kobold Lair for trap sounds, Elements - Horror or Spooky for scary atmosphere, and Shimmering Veils/Disjunction Chamber for places were awe is needed or for chambers with lots of magical auras.
There are a couple false entrances to the tomb, which cause either a rockfall or a sliding stone to block the way/squish slow adventurers/trap them to die. There's a sliding stone sound in Dungeon Depths, and a sound of heavy falling stone in Red Dragon City Raid, specifically the crumbling building one-shot.
The Tomb is rife with pit traps, starting with the first corridor - the "trap sprung" sound from Dungeon Depths, maybe combined with "dagger pierce" sound from Mersial - Female Rogue, or just the "weapon impact" universal one-shot for pit spikes. Perhaps a universal "Wilhelm scream" for the unfortunate PC who doesn't detect the trap. The Kobold Lair also has some useful trap sounds for the various traps.
The mist-filled doorway could be enhanced by the "apparition" mood of the Elements - Horror soundset. The teleportation effect that can be represented by the "teleportation activation" in the Hell soundtrack.
If your players are foolish enough to stick a limb (or a head) through the mouth of the Face of the Great Green Devil, honestly I wouldn't give them any other sound than some screaming. The "psycho screams" of Abandoned Lunatic Asylum or the "ouchy noises" from Tavern Brawl might suit.
If someone ends up in the Forsaken Prison (poor sod), I'd use some "lonely wind" from Elements - Wind to underscore their wretched solitude. If they manage to flip all the levers, use some of the trap sounds from Dungeon Depths or Kobold Lair.
For the Gargoyle Lair fight, you could use the "Sins of the Saviors part 5 & 6" which has a "stone golem" mood. Or just the Ogre set with some wingbeats and claws from Dragon Battle. Or even just the Dragon Battle, minus the deepest growls and breath weapon sounds.
Complex of Secret Doors - pull out your trap sounds again, because there's going to be a lot going off! The poison dart trap from Kobold Lair will be helpful here. And some "tension level" music from Elements - Horror to make things more urgent.
Great Hall of Spheres - Fooling around with these secret doors will possibly get someone teleported back to the entrance, naked, so have your teleport sound from the Hell set ready. Also some of the doors are false and trapped, so trap sounds ready again!
Three-Armed Statue room - There will be a lot of gem-crushing, so the "tumbling rocks" sound from Mountain Pass might be useful here.
Room of Three Chests - Poison dart traps again (that dastardly demi-lich) along with asps and giant skeletons, oh my! Mountain Pass has "lizard hisses" for the snakes, and Undead Battle should serve your skeleton needs.
Chapel of Evil - There's multiple spell traps here, so check your universal spell one-shots, as well as the spell effects in Ezren - Male Wizard. There's also some gas traps, and Elements - Horror has several "mist" sounds that will be useful.
Locked Oaken Door - There are sounds in Dungeon Depths for smashing the door (and in Friendly Tavern for the audible glammer/ghost sounds) and the tilting hallway, and then sounds of lava/melting flesh in the Hell set if anyone falls into the flames below the hallway.
False Crypt - Undead Battle will serve you here, and when the room begins to "collapse", using the "tumbling rocks" from Mountain Pass, and "crumbling building" from Red Dragon City Raid. The "deep mountain rumble" from Ettin Battle will also help sell the illusion. If you have the Sci-Fi player, Natural Disaster's "earthquake" will be great too!
Agitated Chamber - the "deep mountain rumble" from Ettin battle, would work here to show the tippiness of the room, along with some squishy sounds from Ooze Battle as the green slime and brown mold come into play.
Cavern of Gold and Silver Mists - Again use the "mists" element from Elements - Horror, and perhaps some of the songs from "In the Lair of the Siren" for the siren trapped here.
False/True Door - With the sleep gas already in this corridor, get ready to break out the "sleep" spell sound from Ezren - Male Wizard if anyone fails their save. And then they do fall asleep, time for the "grinding stone" sound from Dungeon Depths to squish the sleepers!
Pillared Throne room - I'd get ready with a spell effect sound from Ezren - Male Wizard, in case anyone touches a pillar and starts to levitate. 2nd level effect, or maybe "magical aura" would work. Your two devil faces will teleport someone, so be ready with Hell's "teleportation" effect. The terrible evil wish ring - have the 9th level spell effect sound ready (or "cause fright" because that one has horrible wailing in it), followed by either the "explosion" one-shot from Gnomeland Security or Goblin Battle. If you have the Sci-Fi player, I also like the "large explosion" one-shot from The Devourer. If the group messed about with the crown and scepter, get ready with more spell effects from Ezren's set.
There's some more undead about in the next room or two, so Undead Battle again! You silly adventurers, did you think you could defeat the wiles of Acererak?
Purple Scintillating Portal - You're attacked by weapons here, so most of this can be done by using Bugbear Battle and just turning off the growls and curses, just leaving the weapon noises. For those poor souls transported to nearby rooms in the buff and are faced with the fountain, you can use the water sounds from the Fountain Room set.
The Valves of Mithril - If someone gets electrical damage, use your electricity spell universal one-shot. If they get teleported, the teleport sound from Hell. But if someone causes the door to bleed, you can use the fountain sounds from the Fountain Room set, or even the "passing a waterfall" one-shot from Flooded Cavern, if you really want to make them worry.
False Treasure Room - There's an effrit here that could be released, so use Elemental - Fire, and add some sword sounds from the universal one-shot if your effrit is armed.
The Secret Door - Use the "grinding stone" from Dungeon Depths here.
Crypt of Acererak the Demi-Lich - There's a good chance someone gets blown up here, so use "explosion" from Gnomeland Security/Goblin Battle or "large explosion" from The Destroyer. The door to the mithril vault will open, and I'd recommend the the "giant door" from Dungeon Depths. A ghost may appear, in which case Haunted Desert House has some great ghostly sounds for such a fight.
When Acererak himself appears (if anyone is so foolish as to touch his skull), he'll be ready to suck out people souls. The Shadow Giants has a "shadow vortex trigger" along with a "magic drain" one shot that should fit the bill. He'll also curse the players and teleport them away, so be ready with a spell effect (Spellcaster - Sorcerer's "runestone" is a nice one) for the curse and the "teleport" one-shot from Hell.
If the party gets into a more knock-down drag-out with Acererak - have your spell effects from Erzan - Male Wizard, or Board Game Player's Spellcaster - Sorcerer ready to go, because this arch-lich means business.
And if they actually manage to defeat Acererak, by all means use the "victory playout" from Breaking the Bones of Hell's Apex of Bone, because the players have ruddy well earned it!