In short, these are cards that effectively combo with themselves when multiple copies enter.  They require other ways to make copies of nontoken creatures, like with Kiki-Jiki, Mirror Breaker, then you copy the token using Ghired, Mirror of the Wilds's ability with your other nontoken creatures.  Red has tons of ways to make nontoken copies, so it's not hard to go crazy with mimicky copy-combos.  They generally occur in loops with stuff like copying Combat Celebrant for infinite combat phases with full untaps, or looping with Village Bell-Ringer or Midnight Guard.  But you also get access to exponential effects that build on themselves in various ways, like with Chancellor of the Forge, or with thievery cards like Coercive Recruiter and Molten Primordial that keep going and going until you have all creatures in play (your opponents' creatures can tap to keep making more and more copies of them).  Even the seemingly innocuous Ondu Cleric goes nutso when you copy it a few times... like, Kiki-copy it, then make four more copies via Ghired... doesn't seem too crazy, but you just gained 91 life.  Beat THAT, Essence Warden!  ;)

It's an interesting thought to go Humans with your build, or likewise to go Elves.  You could even make an argument for Goblins.  Because Ghired is Human, you almost have to include a small assortment of Humans to copy (like Coppercoat Vanguard) that can help boost/protect Ghired, then go heavy on Elves for ramp and extra Elf synergies...?  I mean, the deck can be stupid-strong without going tribal, so adding a tribal backbone isn't necessary, but it can also only help fortify it.  That being said, if going the route of copying mana dorks to amplify their production, you really have to go off-script from Elves to maximize your deck's potency, to get in stuff like Harabaz Druid, Sanctum Weaver, etc.  But the Elves go strong outside of their contributions to ramp, so.......

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White Plume Adventurer is sneaky-good in this scheme.  By itself, it's hard to complete a dungeon and be able to untap each creature you control (although untapping one creature on each upkeep is still useful).  But copy it three times and you can complete Lost Mine of Phandelver, and assuming one of the copies leaves before the end of the turn, you have two copies and the original triggering on your opponents' upkeeps, where you can tap creatures to make a copy and copy it a bunch, then resolve one White Plume trigger, make a bunch of copies again, resolve the next White Plume trigger, rinse and repeat until all your triggers resolve (if you have more than three copies).  It requires a way to create a token on each opponent's upkeep, but there are many ways to do that in the deck.  And if you can't do that, you're still untapping your creatures for blocking, after likely tapping them all to create tokens on your turn. 

That all being said, you'll notice that Seedborn Muse isn't nearly as fun to copy, since it isn't a trigger that can be stacked with multiple Muses in play.  This deck tries to dabble in the extremities that copied creatures can create, and copying Seedborn Muse just isn't "extreme", so its value is relatively limited, albeit still very useful with just one copy in play.  So, as is (in the still-early phases of testing the deck), Seedborn Muse is on the block for being in or out of the deck.  Like, is Vitalize a better card in the deck, being able to double(+) the tokens you've created via Ghired, for only one green mana...?  That could easily mean GG when copying the right creatures, and it makes accessing a wincon easier to accomplish early in a game.  What about Call to Glory and Rally of Wings...?  You can see the dilemma Seedborn Muse presents, where the goal of the deck is a wincon popping out of seemingly nowhere, and the alternative options are cheaper to cast, and can be used at instant speed and/or on your turn (when it probably matters most).  And you can still use one of the instant options for a defensive rally to block if needed.  But Seedborn Muse is also a creature that can be used to tap and create a token, which also matters... oy...

Attack with five Wild Beastmasters and you'll give all your other creatures +31/+31 until end of turn... on attack... yw...

Master of Ceremonies is another sneaky-good card, because it's group hug, and who doesn't want free stuff?  But what happens when you have five of these in play at your upkeep, and you have three opponents (typically, I have 5-7 opponents)...?  That's 15 (or likely more) triggers that will most likely result in a pile of Treasure and a bunch of card draw... to start your turn...

The "Manlands" (i.e. stuff like Blinkmoth Nexus) are a fun addition to the deck, as they provide an extra dual-usage that might go unexpected: when they become creatures, you can tap them to copy a token via Ghired (since they aren't tokens), OR you can make a token copy of the land creature, then copy that token a bunch of times, giving yourself a bunch more permanent lands.  They won't stay creatures, but it's a sneaky way to ramp more lands into play.  Unfortunately, the "best" ones, which are the cheapest to activate to become creatures (only 1 mana), are all colorless lands.  You can step up to a 2 mana activation to have a single color land, or a three or four mana activation for a dual land, but 3+ is getting to be too expensive.  The thing is, you have to activate the land to become a creature, make a token copy of it, then activate (again) the token land to make it into a creature before you can start making permanent copies of it (that don't leave the battlefield before the next turn).  Having to pay the activation cost twice makes 3+ mana too much, considering the lands we would be taking out to put those in.  But paying 2 mana (or less) twice is reasonable.

In the same vein of operation, Llanowar Loamspeaker can let us turn a land into a creature, but there's no benefit to doing this for copying tokens via Ghired, as you could simply tap the Loamspeaker to copy the token instead.  However, if you can make a copy of the Loamspeaker, you can use both to copy lands and ramp pretty nicely.  Tap the first Loamspeaker to turn a land into a 3/3 creature (Maze of Ith...?), then use Kiki-Jiki or something to make a copy of the land-creature, except that the token copy will enter as a land, not a creature.  Then you use the second Loamspeaker to turn the token Maze of Ith into a creature, by which Ghired can let your other nontoken creatures copy it.  Sure, Maze of Ith sin't a source of mana, so it's not ramp, but it's a worthy land to make a bunch of copies of.  And, again, the token copies do not enter as creatures, so there is no "summoning sickness" preventing you from using the lands for mana right away (assuming they aren't Mazes of Ith.....).  This is all a secondary benefit to what is primarily a mana dork.  Use it and copy it because it's a mana dork, but with the added benefit that you can potentially also copy lands later, for mana ramp that is harder to remove.

Natural Emergence is a funny card with Ghired... so, you cast it, it resolves, and it enters play.  Its trigger goes on the stack, at which point your lands are already creatures, so you respond to the trigger by using Kiki-Jiki, Mirror Breaker (etc) to make a token copy of a land you control (and having options is never a bad thing), then make copies of the token via Ghired (which you get to keep as legit land ramp) before letting the trigger resolve.  And that trigger just happens to return Natural Emergence to your hand, making it reusable (assuming it doesn't get countered).  The only thing is that you have to have access to an instant speed creature-copier, like Kiki, and there aren't many, so it's hard to put it in the deck expecting to get to use it.

Similar to Natural Emergence's ramp ability, we have Kamahl, Fist of Krosa giving us access to copying lands for only 2 mana total.  Turn a land into a creature for 1 mana, copy the land-creature, creating a non-creature land token.  Then pay 1 mana again to turn the land token into a creature, then copy it a bunch of times via Ghired.  Spike Tiller performs the land-ramping shenanigans for only 4 total mana, but you can only do it once before having to copy the Tiller to be able to do it again.  Kamahl, Heart of Krosa can also do this for the same 4 total mana, but that 8 mana casting cost is prohibitively high.  Skarrg Guildmage and Waker of the Wilds perform the same land copying tricks for 6 total mana.  For Skarrg, providing trample has its benefits, and it's only a 2-drop, so it's a tempting add.  Waker of the Wilds is probably more of a fifth option, in case you want to add the ability to your deck, but you don't have a better option yet, or maybe if you build the deck to go heavier on landfall triggers.

I have to give Destiny Spinner an honorable mention, because it not only protects your creature and enchantment spells, but, at a high cost, you can use it to ramp land tokens into play, too.  But it costs 8 total mana to abuse it, so this isn't the main reason Destiny Spinner should make it into a deck.  The counterspell protection is quite valuable in a deck that's theoretically built to combo out on your turn, enough to strongly consider Destiny Spinner (and Allosaurus Shepherd) for your deck for that purpose alone.  And then, having the ability to ramp later in the game is just a potential bonus secondary use.

To wrap up the land copying shenanigans, one has to mention Living Lands (and the like), as the static addition of the creature type makes copying lands waaaay easier!  However, it's much harder to remove, making lands susceptible to a creature wipe.  Albeit, something like Split Up then becomes very enticing, likely wiping most of your opponents' creatures and lands.  Otherwise, you're just one angry opponent with a slow start away from a board wipe that resets most of the game.  I think the Living Lands-type cards should be handled with care, and planned out properly.  If you run enough Outland Liberator // Frenzied Trapbreaker types of cards, you can remove a Living Lands yourself, providing optimized timing.

Righteous Valkyrie is a must-have, providing big-time life gain and creature P/T boosts when copied enough times to get over 47 life.  But once you're over 47, remember to boost your entering Valkyries P/T before you gain the life for it.  Like, make three copies of it, gaining 36 life, but note when a trigger gets you over 47 life, because the next trigger to resolve won't be for four life, as the Valkyrie that entered is now a 10/12 creature, gaining you 12 life.  And copy it a fourth time (five total in play), and now you're gaining 14 life times five Valkyries, for 70 total life gained.  A fifth copy nets you 96 more life.  For a 3-drop, this does a LOT of work when you start copying it!

Vryn Wingmare and Glowrider are great to cast "in preparation" to win the next turn.  Suppose it resolves, and you can copy it multiple times. In that case, there's a good chance you both stymie your opponents' abilities to win, as well as protect your ability to win on the next turn (with minimal interruptions).  There are other ways to protect your spells on your turn, but they almost exclusively limit their restriction to only happening on your turn.    Being able to put your opponents in concrete-block boots, in most ways that matter on the "control" side of the game, is pretty powerful.  And you're casting a creature, so all the counterspells that target noncreature spells are nerfed, forcing an opponent to waste a free-cast Force of Will on Vryn Wingmare......?  Honestly, it probably won't get countered.  And then you copy it a bunch and "pour concrete."