My hair likes some weight but have you tried Davines curl building serum? I found that literally 4-5 drops of this perfected my routine. I use it mixed into curl cream (one pump of Jessicurl confident coils plus one drop of the serum mixed in my palm per section raked in, 4-5 sections of very wet hair) but alone it is reportedly lightweight and very effective on fine curly hair.
I was hesitant to purchase such a small bottle for so much money - never before has 4 drops of anything had any effect on my hair.
I tried also the ceremonia pequi curl activator - that's another tiny bottle but works more like a regular curl cream, I need a lot and it's hella expensive but I use it sometimes just for the smell, it's gorgeous. Won't repurchase but it's because it's way too lightweight, if you can get away with using only a little the value proposition might be different. And that scent, mmm.
Oh and I gotta put in a plug for the Garnier Fructis curl scrunch gel, if you've not tried it. It has bizarre instructions, says to scrunch into dry hair? But it's very water soluble, lightweight gel if you use it like regular gel.