Your Poison deck is very close to the generic Speed Poison deck. It should be working quite well for you; I'm not sure how to improve it.
I'd take out 2 SoGs and add in another Arsenic if you have it, simply to make it the official speed poison deck.
Want something different? You can always just go with a different deck. There are plenty of decks out there just as good or better than this one (Graboid-Shrieker, Life rush, speed rainbow, Golem rush, et cetera, et cetera.)
If you have 6 upped Sundials, you can switch them with 6 Congeals, I guess. But you don't have enough electrum for that.