Here's what I have for a proposed Fungal Forge order based on what ya'll have said and my own preferences.
I largely focused my efforts on our aquatic forces, going for a mix of sizes and capabilities, from the Colossal+ Manta Rays to the Large-sized Eels. The Mantas are our heavy hitters, meant to destroy fortifications, engage large enemy units, and serve as carrier units, supplemented by the Huge-sized Orcas and Druid Orcas, while the Eels and Octopi can accompany our forces into structures to help clear them. The Hippocampi are individually somewhat weak, but they can each carry multiple riders, are cheap to produce, and benefit from the Plant-Imbued abilities described below.
The Plant-Imbued template is really the best option for us here, not only because it gives a great array of abilities and makes the creature sentient, but also because it gives them a 1/Day Sunburst SLA. That spell inflicts moderate untyped damage, has a Long range (760 feet at their level), and a massive 80ft radius of effect. It can also inflict temporary Blindness and inflicts extra damage against anything vulnerable to sunlight. Imagine the massed fire from dozens or more Plant-Imbued creatures focused on a relatively small area?
This is going to be a major expenditure, though. If ya'll want to trim expenses, I would remove the supplementary Scholarium instructors first. They're going to be helpful to have, but the guardians and aquatic forces are critically important.
Thoughts, suggestions, etc?
[] Fungal Forge Order: 11th Month
-[] Supplementary Scholarium Instructors:
--[] 30 Advanced Cleric Lotus Leshy (CR9, 7 HD) - 3,600 IM each (108,000 IM)
--[] 30 Advanced Wizard Lotus Leshy (CR9, 7 HD) - 3,600 IM each (108,000 IM)
-[] Heart Tree Guardians:
--[] 52 Verdant Wolves (CR6, 6 HD) - 936 HD consumed
--[] 52 Advanced Lotus Leshy (CR9, 7 HD) - 1092 HD consumed
--[] 26 Druid Creature Treants (CR10, 7 HD) - 4,800 IM each (Total: 124,800 IM)
-[] Flesh Forge Guardians:
--[] 20 Verdant Wolves (CR6, 6 HD) - 360 HD consumed
--[] 20 Advanced Lotus Leshy (CR9, 7 HD) - 364 HD consumed
--[] 10 Druid Creature Treants (CR10, 7 HD) - 4,800 IM each (Total: 48,000 IM)
-[] Aquatic Forces:
--[] 50 Advanced Plant-Imbued Gigantean Manta Ray (CR 6, 12 HD) - 1,800 HD consumed
--[] 780 Advanced Plant-Imbued Giant Hippocampus (CR 6, 2 HD) - 4,680 HD consumed
--[] 20 Plant-Imbued Giant Octopus (CR 10, 12 HD) - 4,800 IM each (96,000 IM)
--[] 20 Advanced Plant-Imbued Giant Moray Eel (CR 8, 7 HD) - 2,400 IM each (48,000 IM)
--[] 100 Advanced Plant-Imbued Orca (CR 8, 9 HD) - 2,400 IM each (Total: 240,000 IM)
--[] 20 Advanced Plant-Imbued Druid Creature Orca (CR 10, 9 HD) - 4,800 IM each (Total: 96,000 IM)
-[] Total Cost: 868,800 IM
-[] Total HD Expenditure: 9,232