(Note that unlock numbers may not be completely correct. They should at least be upper bounds.)

Candle
At 25 candles, a candle will appear. Click lit candles and they go out. They will relight after a while. Click enough candles, and you will get a bonus.

Painting
I do not know of any actions that these unlock.

Black Widow
At 100 black widows, a broom will spawn. Pick it up, then click to swing it. It can hit webs and spiders. Destroy all targets, and you'll get a bonus. You want the swing of the broom to pass through the spider or web.

Skull
After getting the Swords upgrade for the haunted house, swords will spawn. Pick one up, and swing it at skulls. (Aim so the sword stops at the top of the skull.) Destroy enough skulls to get a bonus.

Rat
I do not know of any actions that these unlock.

Book
At 25 books, a spell book will appear in the bookcase. Click it, then find the components to get a bonus: (you will need to leave the front hall to collect some of these)
Bat Wing: Bats (outside) or the vampire in bat form (inside)
Bone Marrow: Any skull or skeleton (there's a skull pile outside)
Brain Matter: The giant brain in the vat (outside)
Bubbly Brew: Witch's cauldron (outside)
Catgut: Cats (outside)
Cloud Mist: Clouds (outside)
Dark Bark: Trees (outside)
Dark Soot: Fireplace (inside)
Dripping Wax: Candles (inside)
Drool of the Beast: The monster in the basement window (outside)
Dry Paint: Paintings (inside)
Ectoplasm: Any ghost, inside or out
Electric Current: The jacob's ladder-type device (outside)
Eye of House: That big eye in the window (outside)
Fresh Turned Dirt: The piles of dirt that zombie hands poke through (outside)
Fur of the Bear: The bear rug (inside)
Hands of Time: Clock (inside)
Moon Beams: Light through hole in ceiling (inside) or moon (outside)
Old Paper: books (inside)
Optic Lens: The butler's monocle (inside)
Rat Whiskers: Rats (inside)
Rotting Flesh: Zombies (outside)
Rusty Shavings: Suit of armor (inside)
Seed of Pumpkin: Pumpkins (outside)
Sliver of Ivory: Piano (inside)
Spider Venom: Any spider, inside or out
Squeaky Hinge: Door (inside), or gate (outside)
Stone of Rememberance: Gravestones (outside)
Web of the Spider: Spiderweb, inside or outside
Witch Wart: Witches (outside)


Door
At 250 doors, a key will spawn. Pick it up, then start opening doors. One door has a monster, which will cause you to lose all door prizes you found. When you just have 2 doors, this doesn't matter. After you have at least 3, whether to open another door needs a bit of thought. However, because this is the only source of time skips, and a time skip is much more valuable than the other prizes, my strategy is to keep opening doors until I either find a time skip or the monster.

Clock
At 100 Clocks, 4 scraps of paper can appear. Click all 4, then click on the clock and set the time as shown to get a bonus.

Piano
I do not know of any actions that these unlock.

Ghoul
At 300 ghouls, a hanging skeleton will appear. Instead of using swords on the skulls lying around, they can be used on the skeleton. Three hits are needed to break it apart, and then it needs to be re-assembled. Hints:
* Start with head, ribs, and pelvis.
* Legs have a ] [ shape to them. Arms lack the lower bit.
* Arms are thinner than legs.
* The left side is lighter than the right.
* There's a bug where a piece just refuses to be placed, you might not even be able to pick it up after a while. Ignore it and move on. It's in place, it's just the visuals that are wrong.

At 400 ghouls, a butler will appear. Treats will spawn every so often on his tray.
Steaks go to the bear rug
Flies go to spiders
Garlic goes to the vampire
Cheese goes to the rats
Eyes go to skulls or the skeleton
Icecream(?) goes to the ghosts

At 500 ghouls, every so often, a hand will come up from the floorboards and drop off a mousetrap. (It will take it away after a while, so I suggest moving it somewhere else.) The trap needs to be baited with cheese, and then moved somewhere where a rat will step on it. This will get you a bonus. (You can drop it directly on a rat to trigger it instantly, but only if the rat is moving.)

At 600 ghouls, every so often a wisp will appear and fly around. Drop it into the fire to get a bonus based on the color.
Green: bonus?
Orange: bonus?
Yellow: bonus?
Blue: money
Red: tickets
Purple: gem
Red and Purple are worthwhile.

After getting the Haunted Urn house upgrade, a purple urn is placed on top of the fireplace. Hit it with a lot of swords, and eventually it will break, giving you a very large reward.

This is a bit subjective, but hopefully still useful. It's ordered roughly in the order you'll want to buy these.

Auto collect: This lets you hold more than one random drop at a time.
Auto collect slots: get a couple of these.
Hidden spawn 30 s faster: get a couple of these as well.
(These can be considered an investment. They let you collect more random drops, which include gems.)

Bonus speed length x2
Bonus income length x2
(There's two of each of these, you want both. These let the speed and income stick around longer, and so give you more money.)

Piano Income x2
Ghoul Income x2
(Again, two of each of these. These two give you the majority of your money in the game, so doubling their output is really good.)

Wisp, Broom, Sword, Butler, Spell, and Key upgrades
Just get the first level or two of most of these, and only once they show up. The key upgrade should be fully upgraded, as it's the main source of time skips. Butler treats should be fully upgraded, as you get 4 treats after a time skip.

Show all $/s +10%
Show Piano $/s +10%
Show Ghoul $/s +10%
(10% bonus income. Neat.)

Nice to have:
Autoclicker, mostly for the clicking achievement.
Easier skeleton assembly, if you're going for the achievement.
Double sprit bonus. Expensive, but doubles income.

Once you've gotten most of the upgrades, either save up for the double spirit bonus, or just get a bunch of 6 hour time skips.

It is not possible to sustain scratch tickets in the same way you can sustain spins outside. The game tells you what tickets are present, but not the order, so you could theoretically use the x10 toggle to get x10 tickets whenever the expected return is above 1. Gem tickets have an expected return of about 2 tickets, ticket tickets have an expected return of about 2 tickets, and warp tickets have an expected return of, let's say, 7+ tickets. This would mean the expected return would be greater than 1 if there were at least 4 gem/ticket tickets, or one warp ticket.

The problem is that the expected return is basically never above 1. The greatest common result is 3 gem/ticket tickets, and while that's technically above 1, it's not far enough above to matter, and is still somewhat rare. Warp tickets are better, but they don't give 10x the reward in tickets if you use them with the x10 toggle, and are significantly rarer. You can buy a golden ticket upgrade, but it's incredibly rare to hit it.