Lands are always a sticky subject for budgets. I included lands I think you can use in just about any RGx decks in the future, the shocklands and the checklands, but there are tons of other lands you could look into. The shocklands Stomping grounds I included are the most expensive cards in the deck. You could easily replace those with any of the following, slightly more budget options: fastlands Copperline Gorge or the battlelands Cinder Glade. To go full on budget, you could include the tribal land Unclaimed Territory, or the super budget, super slow fetches of Terramorphic Expanse/Evolving Wilds. A really reliable, powerful, but expensive upgrade to the deck would be to get 4 of the fetchlands Wooded Foothills. But honestly, that's quite the investment, and I wouldn't suggest it unless you're really dedicated to investing into a powerful modern mana base.
The Dragon Eggs are a little bit durdly, but I included them because there aren't any other good 3 drop dragons. You could add in more 4 drops like more Thunderbreak Regent's, or maybe even some Furnace Whelps, but that runs the risk of you not getting any dragons on board turn 3. If you wanted to substitute them for some 2 drops, you could add in some Dragon Hatchlings which are almost the same thing, but faster.
If your playgroup is usually multiplayer, you could easily drop either some of the Verix bladewings or Thunderbreak Regents for some Territorial Hellkites. This card is insane in a 3 player game. It gets a little worse in 4+, but it's still really really good, but isn't quite worth it in only 2 player.
Draconic Disciples aren't bad, but they're not the best 3 drop dragon ramper. If you wanted to add in something really flavorful and fun instead, get some Sarkhan, Firebloods to replace these. Normally you shouldn't run 4 of any single legendary, but you can run up to 4 Sarkhans if you want since if you draw one while you already have one on board you can just throw it into the graveyard with his +1 loyalty ability.
If either or both of the Atarkas don't suit you, you could consider subbing them out with other legendaries. Because we have lots of things that produce mana of any color, you could easily add in Palladia-Mors, the Ruiner, Vaevictis Asmadi, the Dire, or even Karrthus, Tyrant of Jund (high mana cost, high pricetag, but worth it). Or if you want to blot out the sun with she shade of your wings, throw in a couple Utvara Hellkites, you mad man. All of these options are just there to help push your from stalled into winning.
As for removal, you could easily swap out the Abrades for more Banefires if you don't see very many artifacts in your meta. Other options are Magma Spray if your opponent runs tough-to-kill creatures, or Earthquake if they run lots of non-flying tokens. But be wary of earthquake as it kills your mana dorks too!
Instead of the Dragon Tempest cards you could run the same thing, but on a dragon! Scourge of Valkas is amazing, but our curve was already getting a little high so I didn't add it. But hey, it's casual, so throw this guy in if you want a good time. Nesting Dragon also seems amazing, but I haven't had much time to try it out yet so play at your own risk. Harbinger of the Hunt is very on color, but I think Thundermaw Hellkite is probably just leagues better. Lastly, Glorybringer is also a crazy good card to consider subbing into your 5 slot, and since it's about to rotate out of standard the price should drop soon.
