How far do you cast to the Gills?
I like to keep it under 30'

I don't think I ever got a rise out of a spider or a Dragon fly.

With Rainbow, you want to keep the fly small. I dont know about the hook size or Fly (Gob) size with Gills.
But Crappie are what I'm after. She'd deep fry those pesky little Gills if I brought them home, but its like trying to eat a Porky Pine. All spines!
Show a photo of a couple of your Gill Dries.