Muktol

[[Quillspike]] + [[Devoted Druid]] is "only" an infinite strong [[Quillspike]]:
Tap [[Devoted Druid]] for 1 mana and add a -1/-1 on it, pay 1 mana and remove a -1/-1 counter, using [[Quillspike]]'s ability to give him +3/+3. -> +3/+3 for [[Quillspike]] and +/- 0 mana
[[Wellwisher]] could be replaced with Dwynen, [[Dwynen, Gilt-Leaf Daen]] or [[Rhys the Exiled]] if you want to get modern legality.

Why [[Cabal Coffers]] when you don't have any mana-sinks to use the access mana? It also destroys the modern legality of the deck.
[[Gifted Aetherborn]] and [[Bloodghast]] could be added for some more aggro while 2-x [[Vampire Hexmage]] can take care of anything your opponent uses with counters (including planeswalkers)

You cast [[Staggershock]]' from your hand
You cast the rebound of [[Staggershock]] and copy it with [[Dual Casting]]
At your next upkeep there will be no rebound [[Staggershock]] that you can copy as the version you copied isn't cast from your hand and thus the rebound ability doesn't activate.
Besides, a copy is never cast, so copying anything with [[Dual Casting]] doen't activate [[Kiln Fiend]] or [[Young Pyromancer]]

I would rather use [[Lava Spike]], [[Magma Jet]] or even something like [[Dangerous Wager]]/ [[Risk Factor]] instead of [[Staggershock]].

Then what about [[Hyena Umbra]], [[Spirit Mantle]] (Unblockable!) and [[Daybreak Coronet]]? [[Slippery Bogle]] would be one of the "standard" creatures, used for enchantment decks, and with blue it fits unto this colour-scheme

As far as I could investigate, Jumpstart, Battlebond and Planechase where not Standard legal sets, so [[Kor Spiritdancer]] isn't allowed in pioneer: "All Standard releases from Return to Ravnica forward are legal" (https://magic.wizards.com/en/game-info/gameplay/formats/pioneer)
[[Slippery Scoundrel]], [[Ethereal Armor]] and [[Helm of the Gods]] could be used as replacements.
Also remember that [[Lurrus of the Dream-Den]] has to be in your alternative cards if you want to want to play him as companion. This enables you to pay {3} mana and put him into your hand, and play him from there (https://mtg.fandom.com/wiki/Companion)

If you want to use equipment instead of [[Porcuparrot]] then [[Viridian Longbow]] or Sorcerer's Wand could be worth a look.

A short deck and how to play description would be a nice addition
[[Champion of the Parish]] and [[Elite Inquisitor]] could be worth considering.
Personally I loved the combination of [[Champion of the Parish]] with [[Call to Serve]] and/ or [[Bonds of Faith]]

Neither [[Goblin Matron]] nor [[Goblin Ringleader]] can search for [[Weaponize the Monsters]], his only manasink

When you want something to be unblockable with goblins I would rather use [[Goblin Tunneler]]/ [[Goblin Smuggler]]. Your [[Goblin Chieftain]] can interfere a little bit with this plan, but [[Goblin Piledriver]] and 1 Chieftain still enable you to use Tunneler/ Smugglers ability on Piledriver.
The problem I'm having with 1-offs in decks without carddraw is that the chances of drawing the are very slim (wickeddarkman can surely calculate them, he's the mathematician here ;) ). Personally I favour decks with 3-4 copies of a card per slot for steady play.

I just read the informations on [[Grotag Bug-Catcher]] (which is true for any other card that counts party members) on mtg-gatherer:
To determine “the number of creatures in your party,” check whether you control a Cleric, whether you control a Rogue, whether you control a Warrior, and whether you control a Wizard. The number is the total number of those checks to which you answered yes. Each creature you control can be counted for only one of those checks.

So a single [[Changeling Outcast]] (or [[Stonework Packbeast]] or any shapeshifter) will only count as 1 party creature/ type.

Personally I would reconcider some of your cardchoices. For example [[Frenzied Goblin]] doesn't make really sense to me in a mass-based deck, where a single creature that get's blocked doesn't help you anything. [[Skirk Prospector]] also doesn't really help you as you don't have any mana-sinks to use the surplus mana generated this way.
Some suggestions, based on my own experience with mass-based goblin decks:
[[Goblin Bushwhacker]], [[Goblin Wardriver]], [[Massive Raid]], [[Quest for the Goblin Lord]], ([[Raid Bombardment]])

[[Evolving Wilds]] could be worth looking at.

I just read the informations on [[Grotag Bug-Catcher]] (which is true for any other card that counts party members) on mtg-gatherer:
To determine “the number of creatures in your party,” check whether you control a Cleric, whether you control a Rogue, whether you control a Warrior, and whether you control a Wizard. The number is the total number of those checks to which you answered yes. Each creature you control can be counted for only one of those checks.

So a single [[Changeling Outcast]] (or [[Stonework Packbeast]] or any shapeshifter) will only count as 1 party creature/ type.

I would rather use [[Elvish Archdruid]] instead of [[Elvish Mystic]] and [[Llanowar Elves]], as he is also a lord and gives all your elves +1/+1.
Wren's Run Vanquisher and Talara's Battalion could be interesting additions while [[Imperious Perfect]] serves as another lord that also can produce warrior tokens.
Another way to approach this would be [[Hardened Scales]] which doubles the effect of [[Bramblewood Paragon]], or [[Doubling Season]]/ [[Primal Vigor]], which are more expensive to play but also affect your token-producing effects.
Last you could add [[Harmonize]] to get some carddraw, so that you don't run out of things to throw at your opponent.

I don't know how the prices on tcgplayer are shown/ calculated, but when you at the different versions of a card here ate MTGVault there is a difference between the versions. For example [[Painful Lesson]] costs 0.15$ in Amonkhet while the Battlebond card you added to the deck costs 0.20$. So how do you calculate the price?
[[Grimdancer]] could be a very versatile card here.
[[Foreboding Fruit]] could be a cheaper replacement for [[Painful Lesson]]. If you don't need the "target player" but "you" then [[Live Fast]] could also be an option.

A short deck- and how to play description would be a nice addition
Personally I love [[Sylvok Lifestaff]] in budget sacrifice decks. Sure you'll have to pay {1} before you sacrifice something, but getting 3 life for a dying creature can put some pressure on many decks.
[[Tragic Slip]] could be at least be a sideboard option to take care of big, indestructible or big and indestructible creatures.
If you want a more stable increase in power rather than a one-time push, then you could take a look at [[Bloodflow Connoisseur]] instead of [[Bloodthrone Vampire]]. Another option would be [[Falkenrath Torturer]] tough that would require more human based sacrifice targets. (e.g. with [[Doomed Dissenter]], [[Loyal Cathar]] or [[Pit Keeper]])

[[Cubwarden]] or [[Leonin Warleader]] could be worth considering, tough it will be hard to remove something for it, as both are cmc4 cards and you wan to be this deck to be rather fast.

Works like a charm with ETB creatures like [[Kruin Striker]]

I wouldn't use [[Lochmere Serpent]] as finisher because you will need 6 mana every turn to re-cast [[Thopter Assembly]] to lock your opponent. I would rather rely on something cheap, with evasion of one sort (flying, unblockable, menace, intimidate), that brings you additional benefits: [[Nighthawk Scavenger]], [[Vampire Nighthawk]], [[Vault Skirge]] and so on.
You could use artifacts like [[Armillary Sphere]], [[Mycosynth Wellspring]], [[Renegade Map]] or Traveler's Amulet to speed up your game. Those can be fed into [[Time Sieve]] afterwards if you don't have the 5 thopters you need.