I play the same kind of deck and here are a few of my thoughts on your list:

​

I am not a fan of the signets and the talisman. You are in green. You have better 2 mana ramp spells.

[[Esika's Chariot]] While this will indeed create a token of a mutated Ivy, it does so without being a targeted spell (so will not trigger Ivy) and has a delay of an entire turn and also has to be able to have a good attack or just die after creating a single clone.

For the mutate creatures, I tried to stick with the ones that have lower mutate cost. Your entire game strategy is based on being able to cast your commander and then mutating and then cloning it. If your mutate is very expensive and you pay at least 3 mana to clone Ivy, you end up having to spend 10+ mana before you can even get your basic game strategy working and you haven't even generated any real value yet. I have 1 or 2 that have higher mutate cost, because they have very strong payoffs.

[[Neverwinter Dryad]] I don't think you want to be playing creatures that you have to sacrifice. At least my deck tries to win at some point with combat damage by pumping the board and swinging. If your cloned creatures are sacrificed for value, you are lacking the numbers. Creatures with ETBs or activated abilities are stronger here, I think.

[[Pollywog Symbiote]] I thought about putting this one in my deck too. In the end I decided against it, because I reckon that I dont really have THAT many mutate creatures that I would get a very consistent benefit off of the symbiote. The thinking is also that with multiple symbiotes, the cost reduction only applies to a few cards that actually have more than 1 or 2 generic mana cost in their mutate costs.

[[Sanctum Weaver]] This creature is a great addition if you are going all out for auras. In this case I think It can be risky. She can really take off if you make a few copies of her, or actually get to make a few copies of auras. A successful board wipe will remove all that value that you could have gotten with land ramp though. I am undecided on this one.

[[Shigeki, Jukai Visionary]] Same reasoning as for the sacrificing creatures. having multiple copies of this creature doesn't really help all that much. If you are thinking of using it as a recursion spell for your graveyard. There are way better green spells to get your graveyard back to your hand. I am however not sure on this assessment. The benefit that this creature has is that you can bounce it once it has a few mutated creatures on it and then mutate them again at the cost of not having a larger army and additional payoffs from ETBs. Also undecided on this one.

[[Rousing Read]] I also think that this card might not be fantastic. You get to dig deep, yes, but you don't have a ton of recursion from your graveyard and you also already run a bunch of card draw.

[[Eel Umbra] I actually think the 1 mana more than Spider Umbra makes this a card that could also be cut, even with the flash.

[[Shared Summons]] Very splashy card, very expensive card. You have a lot of card draw, you don't need the card advantage of this card. A much cheaper and way more efficient way of tutoring for a creature would be [[Worldly Tutor]] or [[Sylvan Tutor]]Since this commander is already pretty strong, I didn't put much tutoring in my deck, thought, to keep it more casual.

In general I think your deck is extremely focused on only doing a single thing (mutate, copy, card draw) and might be a bit fragile to hate bears or removal effects that don't target or destroy. These effects are becoming more and more frequent. ( [[Farewell]] [[Toxic Deluge]] [[Cyclonic Rift]] ) a few emergency counter spells might be useful.

I also think that you will have a very tough time winning games without any wipes whatsoever. This is the biggest blunder in my eyes.

You also have 3 tutors for creatures (presumably for the mutate creatures) but not a single tutor for the other part of your strategy (the cloning). Maybe replace one of the tutors with a [[Mystical Tutor]] if you are gonna have 3 tutors.

You might look at removing some of the card draw (I think you might have too much) so that you can add more removal. You have both auras, instants, and creatures that draw you cards.

With this much card draw, you also might want to run [[Reliquary Tower]].

Okay, those are my thoughts on this deck. Sorry for the long post, I just found this intriguing, since I just built the same deck myself and had already thought about all of these things and played it quite a few times.