Aviarry

Sorry but Hollowhenge Beast isn't standard...

Well, the most expensive card here is Legion Loyalist: 4.30$ which x4 is 17$, exactly the amount to make this deck under 20$.
You could try replacing him with Bomber Corps or Dynacharge, though it won't be as good as him...

it's the personal sanctuary

take out a few cobbled wings, you don't need that many.
if you want to use odric quickly then Bloodhunter Bat isn't going to help you much.
your knights have exhalted but you want to rush your opponent with a lot of creatures.
whats Urgent Exorcism and angel's mercy for?

Devil's Play?

Izzet guildgate instead of Caldera Lake.

Dark Prophecy?

you could use propaganda/ghostly prison or even crawlspace instead of Norn's Annex

Fiendslayer Paladin
Archangel of Thune?
Path of Bravery

Druid's Deliverance
Hour of Reckoning
Nomads' Assembly
Intangible Virtue
True Conviction
Champion of Lambholt

Golgari Decoy

gutter grime

tooth and nail?

replace sheltering word with Ranger's Guile. 1 mana less.

i'd suggest putting a way of drawing cards

Mana Web .

Stonehewer Giant?

maybe Spirit en-Dal cause it's practically unblockable and can be used to make other creatures unblockable.

Alpha Authority?

you could replace Coal Stoker with Priest of Urabrask