I decided to make casual decks based on the two worst sets in the history of MTG. In order to make it so that the decks weren't completely terrible, I allowed myself to have 25% of the non-land cards be outside of Fallen Empires or Homelands.
For your Saproling deck, don't forget Night Soil and Fungal Bloom as ways to accelerate your Saproling production and spore counters. Icatian Moneychanger looks like the worst card in that deck, filler? Aeolipile is maybe the best removal in the set. Again, because of a lack of removal and interactivity with the opponent, Deathspore Thallid might be a good choice for an out-of-set card. I think that would let you cut white completely because all it offers is that clunky Proliferate + Javelineers interaction to really slowly ping things for 1, while Deathspore can do the same thing more flavorfully.
If you find the Thallid deck underpowered, another option for Fallen Empires is monoblack Thrulls. Black is OP:
Yeah the Javelineers and Moneychanger are in the deck for the proliferate theme. I do like your Fallen Empires deck. I'll probably add in Deathspore Thallid.
For Homelands, I'm removing 2 Giant Albatross and adding 2 Baron Sengir. Way back in the day, my LGS had a Homelands booster draft. I came in 2nd place with a Roterothopter and a Feast of the Unicorn. That should help explain why I took the deck in this direction.
4 Thelon of Havenwood
4 Thorn Thallid
3 Feral Thallid
4 Thallid Devourer
4 Spore Flower
4 Thallid
4 Icatian Javelineers
4 Icatian Moneychanger
2 Pir, Imaginative Rascal
3 Contagion Clasp
Lands (24)
7 Forest
3 Swamp
2 Plains
3 Sunpetal Grove
3 Woodland Cemetery
3 Hickory Woodlot
3 Gemstone Mine
4 Roterothopter
4 Sengir Bats
4 Giant Albatross
2 Giant Oyster
3 Fallowsage
2 Memory Lapse
4 Counterspell
Enchantments (10)
4 Feast of the Unicorn
4 Koskun Falls
2 Endless Scream
3 Feroz's Ban
Lands (24)
10 Island
10 Swamp
4 Drowned Catacomb
If you find the Thallid deck underpowered, another option for Fallen Empires is monoblack Thrulls. Black is OP:
4 Basal Thrull
4 Order of the Ebon Hand
4 Mindstab Thrull
4 Necrite
3 Thrull Champion
2 Ebon Praetor
4 Aeolipile
4 Hymn to Tourach
2 Soul Exchange
2 Tourach's Gate
3 Breeding Pit
4 Ebon Stronghold
20 Swamp
In Homelands, it might be worth 2 Ihsan's Shade or 1 Baron Sengir as a curve topper, because the rest of the creature pool is just so awful. You could also try Black Carriage backed up with Sengir Autocrat. Clockwork Steed is also a decent threat.
For Homelands, I'm removing 2 Giant Albatross and adding 2 Baron Sengir. Way back in the day, my LGS had a Homelands booster draft. I came in 2nd place with a Roterothopter and a Feast of the Unicorn. That should help explain why I took the deck in this direction.
4 Roterothopter
4 Sengir Bats
3 Baron Sengir
4 Ulvenwald Tracker
4 Shrink
Artifacts (3)
3 Serrated Arrows
Enchantments (14)
4 Feast of the Unicorn
3 Primal Order
2 Torture
3 Frontier Siege
2 Endless Scream
10 Forest
10 Swamp
4 Woodland Cemetery
Here is the updated Fallen Empires deck:
4 Thelon of Havenwood
4 Thorn Thallid
3 Feral Thallid
4 Thallid Devourer
4 Spore Flower
4 Thallid
2 Pir, Imaginative Rascal
3 Deathspore Thallid
4 Aeolipile
Enchantments (4)
4 Fungal Bloom
Lands (24)
12 Forest
5 Swamp
4 Woodland Cemetery
3 Hickory Woodlot