Hi. How can i set number of samples per material?
You can’t do that. You can only set the number of samples for the whole rendered image. You can also tweak the number of bounces for the whole scene and some very specific types of materials, not specifically one of the material you made. Any way, the number of bounces has nothing to do with the number of samples…
However! If you use multiple layers, it should be possible to render each of them separately, i.e. with different samplings and to re-compose the final image. It can work for a static image but it would be quite a tedious work for an animation, I think.