* The average cmc of your current iteration is 3,43 and you don't seem to be running many sources of ramp. My first iteration of Muldrotha was lingering around cmc ~4.00 with 8 to 10 sources of ramp and still played like a more expensive
Meren of Clan Nel Toth, as I simply did not have enough available mana to make full use of her ability. I have since lowered my curve to around ~3,00 to have a more consistent early game as well as a more flexible and resistent late game.
* You are already running
Vampire Hexmage, adding in
Dark Depths would give you repeatable access to 20/20 tokens.
* I recommend replacing
Reclamation Sage with
Caustic Caterpillar, as both of them effectively cost the same amount of mana (2G vs 1GG), but
Caustic Caterpillar has the advantage of being a turn 1 play and an instant speed response.
*
Blighted Woodland never seemed to be worth including in any deck to me; paying essentially five mana for two lands is a hefty price.
* Similarly,
Horizon Spellbomb is an all around worse version of
Wayfarer's Bauble, as it adds the land to your hand instead of ramping you.
*
Mind Stone is a lower cmc replacement for
Orazca Relic, which doesn't require the city's
blessing.
* Interesting alternatives to
Clever Impersonator with different downsides are
Phantasmal Image &
Sakashima's Student.
* Since you are running so many snow permanents,
Ice-Fang Coatl could be a neat addition; it is essentially a simic version of
Baleful Strix.
Into the North is another ramp spell you gain access to.