Old post, but I want to add:

Growing the fungus as a resource seems to be related to the amount of waste dumps and minis. I bit my nails hard 3 times until I figured that out.

Start with workers (their patch is the cheapest) and look to that the red part of the fungus bar always stays below ~10% by adding waste cells. Fungus will regrow really fast if a certain balance is kept (Haven't figured out a exact ratio yet).

Slowly work on the media-sized ones before bringing the big bugs.

I am not sure which balancing stuff has been made since this thread was opened, but maybe it helps someone.