Muktol

[[Impaler Shrike]] could be an option tough it only enables you to draw cards after it dealt combat damage and not when it dies, which makes it a little bit unreliable against removal.

[[Order of the Stars]] is a defender often overlooked by players because of it's low toughness, but in my personal opinion protection from a colour levels this. Hard to remove, it can deal with any damage it receives (only trample is a problem) and able to bypass your opponents defence.

[[Coral Colony]]/ [[Doorkeeper]] as alternative win-con?

[[Monastery Swiftspear]] and / or [[Dwarven Forge-Chanter]] would fit here, both are more or less "standard" cards in pauper burn.
21 lands seems to be on the high side for a deck that uses so many cmc 1 and 2 spells, personally I would try to reduce them by 1-3. Playtesting should quickly show the right number. [[Evolving Wilds]] could be replaced with [[Maestros Theater]]. Advantage is that you get 1 life, drawback is that you cannot sacrifice any time you want to.
[[Behold the Multiverse]] could be used instead of [[Lórien Revealed]]. Foretell allows you to cast it in 2 parts, reducing the mana you need at 1 time. It also allows you to scry 2 before you draw, drawback is you only draw 2 cards.

[[Pestilence]], [[Pyrohemia]], [[Court of Ambition]], [[Dogged Pursuit]], [[Palace Siege]]?

[[Illusionist's Bracers]], [[Magewright's Stone]], [[Thousand-Year Elixir]], [[Instill Energy]]

[[Mechanized Production]]?
A deck description would be a nice addition.

[[Cauldron of Souls]] could either further enhance the synergies or serve as additional part of the toolbox you can search for.

[[Cauldron of Souls]] (Probably out of budget range) or [[Resurrection Orb]]?

What about [[Familiar's Ruse]] or [[Moon-Circuit Hacker]]?

"... to reuse your mana..." is a way better description for this :)

Most of my suggestions are from the pauper format (commons only) but you can extend the search on your own.
Spells with flashback, like [[Artful Dodge]] or [[Defy Gravity]] could also be worth a look as it would allow you to re-cast them when you don`t have any cards left on your hand.

Some non-pauper suggestions: [[Guttersnipe]], [[Young Pyromancer]]

Last, as you will need a stable mana-base I would also add some dual-lands: [[Swiftwater Cliffs]], [[Wind-Scarred Crag]], [[Cascade Bluffs]], [[Izzet Boilerworks]]

[[Martyr of Frost]] or [[Judge's Familiar]] instead of [[Spiketail Hatchling]]?

[[Decanter of Endless Water]] could be an idea, to be able to have more cards in your hand.
With all the draw and discard effects you could take a look at some madness spells: [[Obsessive Search]] or [[Just the Wind]].

How should [[Hidden Strings]] help you with casting spells multiple times? The only thing would be [[Gigadrowse]] and untaping some lands.

[[Basilisk Collar]], [[Gorgon Flail]], [[Gorgon's Head]], [[Quietus Spike]]

[[Bloodthirsty Aerialist]] instead of [[Malakir Familiar]]?

When going for heavy hitters have normally used green and [[Axebane Guardian]]/ [[Overgrown Battlement]] to speed up things, tough that would require a remodelling of the deck in this case. Another card that would fit into the white-blue-green colour-scheme would be [[Arcades, the Strategist]]

Fetchlands have some advantages and some disadvantages. Disadvantage is that they mostly enter tapped or have some other drawbacks, which slows your game a little bit. Advantage is that they can fix your mana so you have the right mana in the right situation and they also remove lands from you library, which increases the chance of drawing non-land stuff.
Another disadvantage, tough more for the deck-building than the actual strategy and behaviour of the deck: They are normally rather expensive. The card I suggested isn't that expensive, because it comes from pauper (commons only) but if you look at other fetchlands you can might need t invest a couple of bucks to get them.

I would try to increase the number of [[High Alert]] in the deck. If an opponent manages to destroy it you are stuck with a few ( I would even say too few) creatures that can attack.
[[Coral Colony]]/ [[Doorkeeper]] could be worth a look, because it can convert the deck from beatdown to mill. [[Obscura Storefront]] can help you with mana-fixing.
In general I would try to reduce the number of different cards in the deck, identify key-cards and try to increase their number, so you get some consistency in play.

Two rectangular brackets before and after the name: [[CARDNAME]]
Only drawback: Names with an apostrophe in their name don't work, e.g. [[Archers' Parapet]]

[[Urban Daggertooth]] proliferates each time he is dealt damage.
[[Iron Apprentice]] is an interesting creature as you don't loose it's power if it dies, and in comparison to [[Servant of the Scale]] its non-human.
[[Duskshell Crawler]] gives trample to all your creatures with a +1/+1 counter.
[[Serrated Arrows]] can slowly bleed a creature to death and with some proliferate in the deck you shouldn't run out of counters too fast.
[[Smell Fear]] would be a solid removal with proliferate.