I'm not sure tbh pal, but if you get a cheap filter it can totally mess up your photos. I own a Hoya polarising filter, most people seem to rate them - cost me about £15 I think. Can get a bit expensive though, so it depends how much you want to spend. Next on my list are probably some Cokin Graduated Density filters.
I'm sure someone else will be able to give you a decent answer though.