I think people are misunderstanding you, because you're using the wrong terminology. This isn't "local seo" in the sense that you're promoting a local business, because you say in your OP that it's an "e-shop" which clearly means that its not local. I believe what you really mean is that its local to the region, i.e. Poland, so you want to get it higher in google.pl?
If so, then just use normal SEO methods. There's no distinction between SEO for different countries...