ManiacalManiac

Personally I think you could put the Stormbreath Dragon to 2 of and add 1 copy of Empty the Warrens and 1 copy of Tendrils of Agony. They both act as alternate win conditions in the case your Grapeshot or Dragon get targeted by Surgical Extraction or the likes of.
As well one or possibly 2 copies of Past in Flames will help win games.
Lastly Preordain, Ponder and Brainstorm are all upgrades to Serum Visions IMHO.

The main problem budget decks like this one have is the land base as well as good removal.
In regards to the land 4x Sunpetal Grove would be the best option if you have so many basics.
As far as removal goes Reciprocate, Immolating Glare and Smite are decent budget options.

The fact she's indestructible for when Worldslayer goes off along with the Ooze Rosverde would only need 1 other green symbol to turn on devotion.
However Rancor would be another great addition as well.

Covenant of Blood needs to go. It's just not good. Fatal Push in it's place.
Phyrexian Arena instead of Underworld Connections.
Liliana Vess and Archetype of Finality are both to slow for modern in my opinion. I think you would find Geralf's Messenger to be more useful in this build.
Just my opinions happy casting.

I also forgot to inquire about Falkenrath Gorger. As in why not?

I think Nylea, God of the Hunt would be a good addition to this build.

This deck would never be good in modern by adding a few cards cards. It's a tier 2 standard deck at best. ( no offence intended).

I'd suggest replacing Thraben Doomsayer with spectral Procession. The second ability of Doomsayer is pretty much irrelevant if your deck is performing the way it's designed to. So really Doomsayer is just a slow way to get creatures in play.

Sinister concoction is to slow in my opinion I'd suggest Grasp as a budget alternative or Fatal Push for a non budget. I also believe Bloodmad Vampire is to much of a risky investment with Shock being back in standard. Speaking of which 2 could prove useful in the side board. Gifted Aetherborn would be my first choice in place of Bloodmad. It's a great pressure card early on and a decent blocker late game. Drana, Liberator could also be a super star as a 1 or 2 of.
Just my opinions, Happy Casting. :)

I'd suggest another big win condition other then your Linguring Souls and 6 manlands. All of which seem fragile especially the man lands IMHO. Perhaps Geist of Saint Traft or even Sphinx of the Final Word.

Lightning Bolt in place of Searing Spear since it's strictly better. Magma quake needs to go since it kills your creatures which are your main win condition. Bonfire of the Damned is better then Magmaquake in my opinion for the fact it hits only your opponents creatures and also their life total. (Just make sure you draw your cards by looking at them before putting them into your hand for the miracle clause. I've been called on that before).

I would highly suggest switching Retreat to Emeria for Retreat to Coralhelm. The Emeria Retreat is too slow for modern in my honest opinion. The Coralhelm Retreat combos with your Knight of the Reliquary allowing you to put all plains and forest cards from your library into your graveyard in one turn making your Knight very big. If you do decide to go this route I would also suggest replacing the 2 Copperline Gorge for the missing Stomping Grounds. As well I think the Grazing Gladehart would be better off being the missing 2 Knight of the Reliquary. Having the Grazing Gladehart in the side board to bring in against burn could be useful I suppose.

You should really cut Gleam of Authority, it's only setting you up for getting 2 for 1'd. Murder Investigation should also go IMO for much of the same reason. Spectral Procession and Lingering Souls should both be in this build.

I generally never hit myself with a mill card. With all the fetches, 4 Baubles, 4 Mesmeric Orb It's active on T 3 or 4 consistently. Which is fine since Scribe is more of a T4 play along with removal usually.
I also really like the Leyline factor you mentioned.

turn 3 consistently.

Agreed they were fun but they're just too slow. But I'll add in 3 Heart of Kiran instead of Mimic.

The Aether Hubs were in originally to give a bit of energy for the now removed Multiform Wanderer. They still fill the same role for the Harvester now.

Well a deck like this is so fast, If your opponent isn't playing low cmc cards they're dead anyway.

Combustible Gearhaulk has a home in this deck I believe.

Well after a break from MTGVault I'm back. Made a few changes to incorporate cards from Aether Revolt. As well as the banning of Looter Scooter. Still have a lot of fun with this deck. It's not my most competitive standard deck, but probably my the one I have the most fun with.