Looking at the python right now, and Gnoslings do NOT require any building other than the Gate itself.
I've been messing around with the Kahdi a lot in my personal mod; nothing is finished yet, but I have some solid plans for how I want to up the diversity of their gates. For one, I'm going to give them two more unique buildings, for their Elder Council and Pagan Temple. Then I'm going to move Thades to the unique Elder Council + Gate, give them a sort-of Mobius Witch equivalent from their Mage Guild + Gate, a cure disease/divine unit from their unique Pagan Temple + Gate, a potent city defender from their unique Library + Gate, and a Minotaur-strength, mobile cultural defense unit from Obsidian Gate + Vault Gate.
The big thing is going to be that none of their gate units will be potent offensive units (Except Psions, and Djinns and Gnoslings with high affinity); the Vault Gates will provide mostly support and defense units.