In addition to the aforementioned spirt guides (Elvish is likley superior because of Dryad) I really like Ghostly Prison right now. In many respects it is better than moat for a list like this, while still being budget, because:
1 - It can affect flyers
2 - Asymmetrical
3 - Not dead in multiples
4 - Cheaper
5 - Pairs well with other taxes.
I also think some other cards that could be of use include dismember as swords number 5 or even thorn of amethyst as another Thalia you can have in play at the same time. Also what about leyline? It is a very strong card against Oath for a deck that just wants to rush creatures.
Board wipes are the natural enemy of this list and are seeing more play. I wonder if something like Selfless Spirit would maybe not be a good thing to consider if you suspect people are going to be running supreme verdict?
I don't think Ghostly Prison is where you want to go. In fact, I think that the fact that you are tempted to play Ghostly Prison is a very good indicator that this deck isn't very well positioned right now. You want a metagame where you don't fight (many) other creatures. This deck has a hard time beating creature based strategies, simply because our creatures are much smaller.
You don't want to be the deck playing non-creature spells trying to stop creatures. You want to be the deck playing creatures trying to stop non-creature spells.
Oh, you also never want to play Thorn in this deck. Glowrider/Wingmare are much better.