My favorite version of spider spawning is blue-green base with self mill. Hedron crab is the best card in the deck. The deck's only weakness was that it didn't interact well with what the opponent was trying to do, and it could lose to burn/tokens before it got going.
With the new lands from the expansion, I can easily add a white splash to my black splash. Rhox War Monk was the card I was really after, winning most aggro match-ups single handedly, and white actually offers some reliable removal to boot.
The idea is to play out all your creatures that cycle for other creatures, cycling your deck and filling your graveyard while pressuring durdlers and staving off aggro. Whenever you cast spider spawning you win, but it is very possible to win without it.
This isn't a firm decklist but a basic framework to modify depending on the meta. Angelic edit is a great answer to decks that rely on enchantments, but you can swap it out for reprisal if you're not seeing any of those.
I haven't looked at the mana base too closely yet. I'm running a lot of green and blue to cast the important early cards reliably, but it might be too much. If I could add in a bit more black I'd be able to run Shadowborn Demon which would be amazing. Otherwise, removing at least 1 tap land for an untapped land would be a real help. I'm also considering the third Treasured Find and perhaps some Nemesis of Mortals, even though they dilute the theme of the deck.
Any advice would be appreciated.
OK, I would do this:
First off, playing 4 colours in a spider deck is pretty ambitious.
I'd cut white as it really isn't helping your "theme". If you really want to keep white, however, and you are worried about aggro, take out the Quickling (which really doesn't fit theme) and put in Lone Missionary. Also, Masked Admirers, while a pretty decent card in this meta, is slow and not in theme. Same for Mentor of the Meek.
I'd replace it all with a full set of Beastmaster Ascension, both Graveborn Muses (those guys just give you so much gas), 3 of Viscera Draggers (alternately, you could put in Rescue from the Underworld or Treasure Find), the Shadowborn Demon and the Crateroof Behemoth (because if you've never delivered a HOOFING, you haven't really lived...that and it just wins games you shouldn't have).
That gives you 5 must-answer cards that don't even rely on you spawning and that are even better with them.
Personally, I'd drop the white at least and go no more than 3 colour. The Golgari Spawning decks are reliable, relentless, and consistent, where this deck will probably be less consistent overall.