Steel Hellkite has been reprinted often enough that its pretty much a budget card now. Firebreathing and removal on a stick and you can use your Manifold Key to untap it after combat.

Ryusei, the Falling Star is also budget and can give you a 5 point Earthquake if you have a sac outlet of some sort. Speaking of, I'd add a Quake in place of Hordeling Outburst .

Dragonspeaker Shaman is needed cost reduction for your scaled beasties though looking on Card Kingdom.com, the price on this is a bit higher than I would have guessed. Would still be a very good investment for the deck.

Icon of Ancestry is an anthem and search for more dragons.

You really need more artifact ramp here. Budget options [under $1] include: Star Compass , Mana Geode , Pillar of Origins and Hedron Archive . If you're willing to bump up and spend more than $1 per rock: Mind Stone , Worn Powerstone , Wayfarer's Bauble and Fire Diamond are more powerful options. Sol Ring is an obvious choice as well and if you can afford to splurge on one, I would.

By Force is a really nice mass artifact removal spell that will go a long way towards slowing down the table to give you time to launch the dragon airforce.

Too bad on Sundial of the Infinite , it would really make the deck much better by mitigating Zirilan's drawback.