Any recommendations will be greatly appreciated.
I don't personally use ND Grads, as I find it easier and cheaper to add a virtual one in lightroom for a low value, or go full on hdr for a higher value.
Further and more expert opinion below;
Def get a polarising filter. I got a cheapy, kenko I think, and its really good.
Def have a look at grad N D filter. You'll be able to get some really good landscape shots/sunsets(rises)/waterfalls etc. It'll teach you more about using the camera itself also. I got a cokin triple set.