The most useful ND graduated filter is a 3 stop, a 1 stop is pretty limited on it's own. However, I would recommend a full set of 1,2 and 3 stop. If you shoot a lot of mountain or hill scenes (or cityscapes), then a set of soft grads would probably be best, but for coastal a set of hard grads would probably be more suitable. I would also avoid the Cokin filters, although their adaptors are fine. For a similar price range, I would go for Hi-Tech filters instead, as they don't have the noticeable colour cast that the Cokin filters have. I don't know if they're available in all countries though.
UV filters are pretty useless on digital cameras, beyond protection for the lens. If you have a filter set on the lens, you don't want an extra layer of glass in the form of a UV filter. However, a polarising filter would be useful, but be careful with it on wideangle lenses, as you can get uneven polarisation, plus for ultrawides, you can get vignetting or even see the filter edge in frame if you start stacking the filters.