Muktol

Personally I'm using Cockatrice for testing my pauper decks. You can play against yourself, or use the servers to find games. or open games for others to join.
[[Tribute Mage]] and/ or [[Trophy Mage]] only would make real sense to me, if you would add other artifacts, that you could search for, like another combo (like [[Myr Galvanizer]] and [[Silver Myr]] or [[Alloy Myr]], [[Palladium Myr]]) Without anything other to search for that you really need, it would be wasted cards.

I like that. Removing [[Planar Cleansing]] for [[Blinding Light]]? Would be my kind of thought. Only thing is, I suggested for the other two decks, to keep them modern legal...

What about using enchantments and artifacts? This way you can point out the difference between both, when a creature dies. [[Bladed Pinions]] could replace [[Asha's Favor]] (tough you would loose vigilance) or [[Maul of the Skyclaves]] could replace [[Serra's Embrace]] (+first strike - vigilance)

Squeezing an artifact creature into a deck, only to get one into the deck, normally is not a real good idea, tough [[Porcelain Legionnaire]] could work here. But it's white, so you don't have the "teaching" effect when using [[Blinding Light]].

The lashes are more expensive to play, and thus slower, than [[Ethereal Armor]] removed from white, or [[Blanchwood Armor]] (Which I suggested for green), but if each deck would have an artifact or equipment of this kind, it would be balanced. Even without the Warlock, there still would be [[Keening Banshee]] and [[Ascendant Evincar]] with flying, who could carry the lash to the opponent and deal a good amount of damage.

Yes, the wording is quite uncommon today, so a [[Tormented Soul]] might be the better choice. On the other hand, Kazzong really likes this card ^^

Head -> Table -> KLONK ... The only way you can heal a non-thinking head
Thank you for pointing that out :)
[[Trusted Pegasus]] or [[Cobbled Wings]] could be used, white has the second most flying creatures after blue, so this would fit.

I'm not as experienced as Puschkin, but here are my thought on your mono green beginner deck.
The descriptions could be a little more detailed ;)

Mono black and mono white are both modern legal, so removing [[Spidersilk Armor]] would be an idea.

Without [[Gigantomancer]] and [[Pelakka Wurm]] the deck seems to be a sitting duck, just waiting to get shot. You have lot's and lots of ramp (14! creatures), but only those two creatures as finishers, and both black (Removal/ discard) and white ([[Pacifism]]) have way's of dealing with those. My basic advice would be to reduce the ramp, use some spell-ramp ([[Cultivate]]/ [[Rampant Growth]]) to show the difference, and use some additional powerful creatures. I would also include some way of using the excess mana, generated by all your mana-generators.

Here are some general suggestions:
[[Garruk's Packleader]], [[Kalonian Twingrove]], [[Nylea's Disciple]], [[Adventure Awaits]]/ [[Lead the Stampede]], [[Deadly Recluse]], [[Scale the Heights]], [[Trollhide]], [[Primordial Hydra]] (NOT searchable by [[Fierce Empath]]), [[Blanchwood Armor]] (If you want to counter-balance [[Nightmare Lash]] and [[Ethereal Armor]]), [[Primeval Titan]], [[Khalni Hydra]],

Some {X}-Mana Spells. Use Scryfall to find those, MTGVault doesn't have an option to search for {X} mana spells. I add the link to the search I used: https://scryfall.com/search?as=grid&order=name&q=color%3DG+mana%3A%7BX%7D+legal%3Amodern
[[Hungering Hydra]], [[Ivy Elemental]], [[Slime Molding]], [[Stream of Life]], [[Thrive]], [[Untamed Might]], [[Gelatinous Genesis]]

A description is missing ;)
Something that comes to my mind: White doesn't have any means of mass-strengthening their creatures, but black does?

Black does have it's share of unblockable creatures, so [[Dread Warlock]] is OK for me.

[[Dark Banishing]] vs [[Doom Blade]]/ [[Murder]]? I didn't see to much regeneration, so this should be no big point.

[[Life's Finale]] might be a little bit to complicated/ unpractical for beginner players, so I would remove it.

You said that [[Ethereal Armor]] is to powerful in the white deck, I wonder if this might not also be true for [[Nightmare Lash]]. It's more expensive to play, and thus slower, but it's an artifact that you can attach to any creature, and it will stay on the battlefield when the creature carrying it is killed...

With a high number of {B} mana in your creatures costs, you could use [[Gray Merchant of Asphodel]], Some other cards, that are very typical (for me at least) for black decks: [[Chittering Rats]], [[Sign in Blood]]/ [[Read the Bones]], [[Village Rites]], [[Defile]]], [[Eternal Thirst]] (OK, this one is not real typical, but for me it shows the core of black strategy: Kill and profit from it)

+1
I was about to criticise the deck for using [[Knight of Meadowgrain]] wit a first strike ability, then I was looking at my own mono white beginner deck and saw that it used...[[Knight of Meadowgrain]] AND [[Danitha Capashen, Paragon]] AND [[Odric, Master Tactician]]. So much for that ;)

[[Ballynock Trapper]] somehow generates a weird feeling in this deck for me. 4 mana for a 2/2 creature may not look and sound like an efficient white card to beginners. On the other hand all other (cheaper) creatures have a {1} or {W} mana cost (like [[Sigardian Priest]]) to pay...

As for the special lands, Puschkin mentioned (for all your beginner decks), what about cycling lands? [[Secluded Steppe]], [[Barren Moor]], and so on?

I totally agree with Puschkin on [[Brave the Elements]] and colour protection. If you want to protect your creatures you could use hexproof: [[Beaming Defiance]]. To push through damage you could take a look at [[Spirit Mantle]].

White also values companionship, so [[Boros Elite]] might be a good idea. [[Danitha Capashen, Paragon]] can reduce the costs for equipment and enchantments, and would add a legendary creature to the deck, so you could also explain this rule.

+1
What about adding [[Mobilize]]/ [[Vitalize]] to untap all your creatures and use them again?
Two other card, often included in pauper defender decks would be [[Ulamog's Crusher]] and [[Ulvenwald Captive]].

[[Managorger Hydra]] instead of [[Spinal Centipede]]/ [[Vampire of the Dire Moon]]?
[[Doom Blade]]/ [[Cast Down]]/ [[Go for the Throat]] instead of [[Murder]]?
The descriptions could be a little more detailed.

Further suggestions:
[[Cultivate]], [[Aspect of Hydra]], [[Arbor Elf]], [[Utopia Sprawl]], [[Scourge of Skola Vale]]

[[Baral, Chief of Compliance]], [[Brineborn Cutthroat]], [[Lullmage Mentor]], [[Thing in the Ice]]
The deck description could be a little more detailed ;)

+1
There are some things that come to my mind when seeing this combo.
[[Tribute Mage]] or [[Trophy Mage]] could be used to search 2 of your 4 pieces, tough you would need some other artifacts with cmc 2 and 3 to make real use of them. [[Fabricate]] would be another option to search what you need.
[[Confront the Unknown]] would produce you 8 clue tokens and give a creature +8/+8 for only 1 mana, if you have 3 [[Parallel Lives]] on the battlefield. Would be a good carddraw/ finisher.
[[Urza, Lord High Artificer]], golem splicers, [[Myr Propagator]], [[Myriad Construct]]. White also has some good token-producing spells, which would have quite an impact with the combo on the field.

I've done 150+ testgames until now, and one thing I noticed is that [[Crypt Incursion]] can win you games. Even aggressive decks can have a problem dealing with a a sudden lifegain of 30+...which isn't uncommon against creature based decks.
[[Witch's Cottage]] and [[Dimir Infiltrator]] work well together tutoring [[Jace's Erasure]], which works like a charm in combination with [[Pilfered Plans]]
I really wish there would be more cards like [[Merfolk Secretkeeper // Venture Deeper]] or [[Iceberg Cancrix]]. The biggest problem here is is that a 0/4 can slow down aggressive decks, but it cannot stop, or deal, with the threats.

Add two rectangular brackets before and after the cardname: [[Cardname]]

+1
I can only agree to what Puschkin said: That the deck lacks a strategy of staying alive until you're able to execute your plan, based around [[Myojin of Cleansing Fire]] (which isn't a bad plan). Personally I would nevertheless add some protection. because exile or -x/-x doesn't protect your finisher from being removed.

White and blue offers some good proliferate cards:
[[Callous Dismissal]] ... Basically a [[Unsummon]] that gives you a 0/0 with a +1/+1 counter, so it can either be used as as chump-blocker or can profit from proliferate long-term.
[[Unbreakable Formation]] ... indestructible for all your creatures and +1/+1 counters and vigilance when you cast it in your main phase. Sure your opponnent will see what is coming at him, but this won't help him much when you use [[Myojin of Cleansing Fire]]'s ability.
[[Prison Realm]]/ [[Oblivion Ring]]/ [[Journey to Nowhere]] ... simple but effective exile removal. Ring is probably the most versatile, while Realm lets you scry and and Journey is cheap.

But green also has some very interesting ones, and it would also give you access to ramp ([[Rampant Growth]]):
[[Pollenbright Druid]] ...can be used as chump-blocker early on or to proliferate when played late.
[[Servant of the Scale]]/ [[Star Pupil]] ... those creatures let you move their +1/+1 counters to another creature when they die. So when you mass-remove all your creatures, your [[Myojin of Cleansing Fire]] could be able to finish your opponent with one or two big blows.
[[Scrounging Bandar]]/ [[Barkhide Troll]] ... creatures I would call "simple counter preservers". Bandar has the advantage of being able to move it's counters to another creature, but only at the beginning in your upkeep. The Troll is a little tougher and able to give itself hexproof.
[[Snakeskin Veil]] ... hexproof and a +1/+1 counter for 1 mana

+1
What about [[Garruk's Uprising]]? Provides your with carddraw and all your creatures with trample.

[[Rabid Bite]] can be replaced with [[Ram Through]]. Same cmc, same effect, but if you have a [[Pridemalkin]] on the field, you can remove a creature and deal some damage to your opponent.

At the moment it's no big deal as you only have one deck but a link to your deck in the forum would have been great.

When asking for help you should give the users some information to work with, just stating "i need help building a deck" can lead anywhere. I would ask you to write down some informations (In the deck-description for example) on what you want this deck to achieve (the strategy), restrictions (standard, modern, price, editions, and what else you can think of) and any other information you would think that could help the users here to help you.

I was finally able to make some testgames. The manabase was way to complicated and slowed me down to heavy, so I went back to normal. [[Lead the Stampede]] was not really as effective as I had hoped, so back to [[Adventure Awaits]]. [[Young Wolf]] was changed to [[Nest Invader]] because the invader's token can be sacrificed, even when I don't have a [[Carrion Feeder]] on the field.
Against MBC I tried the new [[Leather Armor]], but Ward 1 simply shifts the removal by one turn, and this is not enough.

+1
[[Adventure Awaits]] might be an option instead of [[Adventurous Impulse]] as it digs 5 cards deep instead of "only" 3.
[[Adventuring Gear]] and [[Khalni Heart Expedition]] or [[Harrow]] could get you a very explosive play.

I know the problem with fun-mechanics. They sound great, and if you get to play them, the match can be really funny (at least for you), but often those are weak decks compared to other, more streamlined, builds. I had a draw/discard madness deck once, which was really fun to play as it could drive your opponent nuts when he wanted to play something and you reacted with draw+discard+lets look if I get an answer to your card due to my draw. I would suggest that you make another deck, put the fun-mechanics into this, and let your friends also built fun-decks, that are not absolutely streamlined/ competitive. You could even use some of the unstable/unhinged cards.

Many of my pauper decks with access to black use [[Geth's Verdict]] or [[Diabolic Edict]], at least in the sideboard, some of them even mainboard, as this card can cripple a hexproof deck really fast. What you could do to play around some of those sacrifice mechanics would be the usage of manlands: [[Lair of the Hydra]] (Other colours have access to other manlands as well, but this one is the only green). Your opponents forces you to sacrifice a creature, you react, turn the land into a creature and sacrifice it. Another option could be the usage of [[Jungleborn Pioneer]] as this gives you a hexproof token and a creature that you can sacrifice.
If you're looking for a creature with good survivability and power then [[Thrun, the Last Troll]] could be worth a look, tough he is expensive with 3$+/card.