How Can You Coordinate Curtains with Rugs and Upholstered Furniture?

Our living room has a patterned rug in rust and navy, and a plain grey sofa with a couple of printed cushions. I want to add curtains but I’m scared of it all clashing. My plan is plain or lightly textured curtains in a shade pulled from the rug, with window blinds underneath for the afternoon glare, so no new pattern comes in. Does that sound right? Or should the curtains carry some pattern too? I’d also like to know how much contrast in scale is okay. I noticed Kingdom of Curtains does free design consultancy across India, so I may take photos of the rug and sofa. Anyone solved this before?