Hey, well done with precon upgrade on a budget.

Scion of the Ur-Dragon is one of the best Dragons for Dragon tribal being a repeatable Dragon tutor. Scion could replace Wardscale Dragon. Scion's ability to change into a Dragon can be done at instant speed which means during combat you can change into different Dragons whenever there's a stop at a combat phase.

Scion's ability goes well with Savage Ventmaw, Teneb, the Harvester and Bladewing the Risen which is a three Dragon combo to end up with Scion and cheat Teneb/Bladewing on the battlefield. Then if Teneb lives he can reanimate other Dragons you tutor for with Scion. Savage is part of the combo because you tutor for him first with Scion, before you attack which then gives you 6 mana to activate Scion three times during combat. The combo takes 11 mana therefore Savage making 6 mana means you only need 5 mana for other sources. Would you like me to explain this combo?

Consider cutting a few of the least good Dragons for more Dragon support? Rhythm of the Wild and Temur Ascendancy are in the maybeboard and they could replace two Dragons such as Vorosh, the Hunter and Darigaaz Reincarnated. The repeatable effects of Rhythm and Ascendancy are much better than what these Dragons can provide. Faeburrow Elder is also in the maybeboard and it's a much better ramp source than Mana Geode. Crux of Fate and Eerie Ultimatum are also in the maybeboard they could replace Spit Flame and Palace Siege.

There's 20 lands here of the 36 that will always ETB tapped which is a lot. The Tri lands on a budget are worth always ETB tapped, the rest are not. My advice is cut the Bounce lands and Scry lands for other types of lands. The combination of lots of Tri lands and Bounce lands is not good; play either one, not both in the same manabase.

Exotic Orchard is budget staple Rainbow land. By adding a few more basic lands then the 5 Battle lands are budget options since they have interaction with lots of basic lands. Cinder Glade, Smoldering Marsh, Sunken Hollow, Prairie Stream, Canopy Vista, can get each of these for less than $2 at TCGPlayer with Vista being the most expensive.

Manabase upgrades to consider:

• Add 2x Forest > Temple of Malady and Temple of Triumph
• Exotic Orchard > Temple of Epiphany
• Cinder Glade > Gruul Turf
• Smoldering Marsh > Rakdos Carnarium
• Prairie Stream > Orzhov Basilica
• Sunken Hollow > Izzet Boilerworks

You have Farseek and it can search for one of these Battle lands which is helpful for color fixing.

Good luck with your deck.