My list:
https://deckstats.net/decks/120669/1651239-meren-of-clan-nel-toth-reanimaI'll just go through each category of card.
Lands:
Your land base is pretty good, but I don't think you need so many taplands.
Foul Orchard &
Jungle Hollow are pretty much never worth it, and
Evolving Wilds,
Fabled Passage, and
Desert of the Indomitable don't have any synergy here.
Darkbore Pathway // Slitherbore Pathway,
Llanowar Wastes,
Temple of Malady, and
Woodland Cemetery are some better options.
Ramp:
Your ramp suite is a little light (I only counted 4-5 cards). Meren has a lot of great options for ramp, so here are my favorites:
Arcane Signet,
Golgari Signet,
Talisman of Dominance, and
Elves of Deep Shadow are generically good Golgari ramp;
Wood Elves &
Devoted Druid are popular because of obvious synergies; and
Blood Pet and
Heart Warden are less popular but are personal favorites of mine.
Card Advantage:
You have plenty of card draw pieces, but you are lacking some key ones.
Village Rites is (mostly) a better
Costly Plunder.
Viscera Seer is absolutely fantastic, and deserves an inclusion in pretty much every Meren deck.
Midnight Reaper is similar to
Grim Haruspex, but it triggers off of itself, which is more important than you may think.
Smothering Abomination is fantastic because it is a pseudo-sac outlet and even draws cards off of tokens.
Removal:
Your removal is very solid. I noticed you have
Caustic Caterpillar in your maybeboard, and I highly suggest you include it. It's an extremely good one drop (I personally rate it even over
Acidic Slime because of how self-sufficient
Caustic Caterpillar is).
Otherwise, your list seems to have a high average cmc. I suggest resorting your deck based on CMC and reconsidering whether your higher-CMC cards warrant inclusion. Ex. How necessary is
In Garruk's Wake? Perhaps
Massacre Wurm can do a similar job, without being 9 mana.
Let me know if you have any other questions & I hope this helped!