One of my most useful gloves have been this model Wells-Lamont that you can get at Walmart for about $15http://www.wellslamont.com/index.php/work/117
They have thinsulate insulation and neoprene on the back. They breathe just a little so your hands don't get damp and clammy. I've used them comfortably down to about
Obviously they are not good for the coldest temps and they are made rather cheaply, but they will last at least on year. I think I am on my third season using them.
I have some Castelli Estremos that are MUCH nicer construction, but I don't think they are really actually much warmer. Maybe a little.
And I also have some LG Supershield Lobster gloves for more extreme conditions, but they are very bulky.
As noted above, fit is very important in the cold. If the gloves constrict your fingers it negates any insulation.