Muktol

Probably [[Rile]] or [[Thunderherd Migration]].
With [[Rile]] you will loose a cantrip thah grants you trample as one-time effect, while [[Thunderherd Migration]] already has [[Ranging Raptors]] as possible replacement in the deck.

Tilonalli's Crown could be of interest here.

[[Drift of Phantasms]] could search for [[Laboratory Maniac]] (I would definitely add a second copy of it), while [[Leveler]] could help you to speed up the game a little bit.
Personally I would play [[Rune Snag]] over [[Mana Tithe]]

[[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]])