Having beautiful nails is not just about having a nice color on them. Without well trimmed cuticles and a smooth nail surface to paint on it can look a bit crappy I think, then it doesn't matter if you use an expensive nail polish from Chanel or something cheaper from Rimmel.
Lately I have been using this product, Mavala Lightening scrub mask, and I am very satisfied with it. It is like a peeling for your nails and cuticles and it is also supposed to get discolored nails lighter.
I think it has a good effect on my cuticles, since I started using this a couple of times every week I don't cut my cuticles as much. It also creates a smooth surface on the nails which I like.
My nails are not so discolored so it is hard to say if it helps against it.
But I absolutely recommend this.