[[Lightning Bolt]].
[[Dark Tower]], [[Lone Tower]], [[Gothic Tower]] give you decent tempo for a [[Forsaken]] turn 1 or various 3 drops turn 2.
Threats: I like [[Forsaken]] more than [[Land Surveyor]]. Apart from the fact that Surveyor is a much worse draw later on, it still doesn't shine early. At its best, Surveyor is "(2) for 1/1" that doesn't cost a card. It's not terrible, but it's also not a good threat or an efficient way to spend 2. If you want a land, just draw a land, no need to pay 2. Efficiency is key for Witch, so I choose [[Forsaken]], which doesn't die to [[Vile Imp]], trade against other 3/3 charge, and is not a dead draw later on. Admittedly, [[Kettletop Leprechaun]] exists. It's better than [[Land Surveyor]] but can still be unreliable as an attacker / drawing site. Witch needs to play sites every turn and then stop drawing them almost completely, so there is little room for Kettletop to get the site on time.
[[Sphere of Animosity]] is another redundancy against healing.

Minions

Since a lot of them are staples (or just self-explanatory), I will only talk about the few notable ones.

[[Forsaken]] this card is the definition of efficiency. Being in the void also means it's harder to kill, making opponent's turn more awkward. Later in the game, this can pop in right next to an enemy site.
[[Skeleton Mage]] I mention [[Land Surveyor]] earlier, and this card is comparable to Land Surveyor since it's also a "(2) for 1/1" that doesn't cost a card. The difference is the card that it "draws" will always be relevant at any stage of the game. Plus, it provides better positioning for [[Firebolts]] and [[Minor Explosion]]. If you and your opponent have more than 1 spell in the cemetery, this is also a card selection. The downside is that it's not a great draw early, but you can also just mulligan it away or hold it for late game, so it's not really a downside.
[[Phase Assassin]] I'm not so sure about this one. It has evasion and great positioning for a fair stat. That should be good enough for when you want to be proactive. Stealth is also good with [[Boudicca]], [[Torshammar Trinket]]

Magic

[[Firebolts]], [[Lightning Bolt]] They're sometimes good enough to just burn your opponent directly on turn 2, but it's not an ideal play against other aggressive decks.
[[Gift of the Serpent]] Pairs well with [[Colicky Dragonettes]], [[Quarrelsome Kobolds]], or allow you to trade up your random 1/1, 2/2.
[[Blaze]] is finisher + positioning.
[[Minor Explosion]] Always feels good to 2-for-1 with this. It's harder to play around at Death's Door than [[Lightning Bolt]]. Also ordinary, so [[Skeleton Mage]] can get it.
[[Infiltrate]] is a good tempo play to save some life and get one hit in. Good with [[Boudicca]], [[Torshammar Trinket]].

Site

[[Open Mausoleum]], [[Molten Maar]] for card advantage.
[[River of Blood]] You can try to mulligan for this against control.
[[Poisoned Well]] works nice with [[Sinkhole]]
[[Spore Spouts]] help you get in with [[Vile Imp]], [[Hotwheel]], [[Quarrelsome Kobolds]] for Death's Door.

Death Wish