The type depends on the roads you´re going to take (road bike for paved roads, mountain bike if it might be offroad). I fitted my bike with carriers for bags. This helps to lower the center of gravity and makes the bike more stable. There are different grades of spokes. I´d take heavy duty stainless steel spokes to compensate for the increased weight. I also wrapped the crossing points of the spokes with fine wire. The wheels are a little stiffer and if a spoke breaks it will stay in place. I prefer tires with a kevlar carcass. They are less prone to puncture.
I have a couple of spare spokes taped to the pump and at least one spare tube. For longer tours I pack a spare cable for the brakes.