As mentioned above, your hands will get wet, no matter what. So you need good insulation. Maybe most important will be the ability to get your gloves off and onto your wet hands when the gloves themselves are soaking wet. The best gloves I've found so far are the Giro 100 Proof gloves. Some people do fine with ragg wool gloves and some sort of windproof cover, usually leather, but could be anything that allows you to operate the bike.