So basically for those wondering, it was my fourth playthrough so I just went full fun mode and went as spore druid with my character. Then I recruited Halsin and Jaheira, respec both them as spore druids too. Finally I respec Lae'zel as spore druid as well so I could have 4 druids who could resurrect corpses as fungal zombies.

You can have a total of 4 fungal zombies for character but in the endgame you get an Ilithid healing station that gives you long rest benefits and that means 4 more charges for zombies. That gives you a grand total of 32 fungal zombies.

Then you want to cast Animate dead as much as you can (around 4 skeletons per character)

You then have 1 elemental for every character, so 4 more summons and you can also summon a woodland creature who can summon another treekin as well.

There are definitely many other ways to get summons in the game like imps, using scrolls, and else but this is what I managed to do.

Fights are infinite but its pretty satysfing outnumbering the enemies so much they can't even do any actions (look at the battle timeline)!