Resources should not be value-less
Currently, when doing trading with other nations resources possessed by your rival have a large amount of worth. Resources that you offer to your rival currently have no value and cannot be used in trades or even as gifts to allies or treaty-holders sorely in need of that resource. This should be changed. Either:
1) Give them some appropriate monetary value or
2) Remove them entirely from your side of the trade screen.
If having no worth when you are offering the resource is an intentional design decision then make it very clear that this is intentional. It does you no good to hide that fact and confuse players. If it is not an intentional design decision, then it should be fixed.