Originally Posted by Yunalicia
Lining (even if very light) can weight down your pants and change the drape and fit of them.
But if the fashion fabric is very thin, that can be a good thing!
@OP - It's hard to say without seeing the fabric and the reference image. If the pants are supposed to be flowy, then maybe just wear tights or hose underneath. If they are supposed to be more like suit pants, then you might want to line them. I've never seen pants lined with anything other than the type of material Koumori has described. While some lining material can be expensive (i.e. China Silk that is actually silk) most acetates and polyesters run $2-$3 a yard.