You sound very eager, so I thought I'd post an answer that will hold you until the real dressage experts show up.
What the judges are looking for at the walk is an active, free swinging walk, with the horse moving well under himself and straight, and accepting the contact happily. At the free walk, all of the above, plus stretching forward and down into light, passive contact. The critical moment is the transition from free walk back to working walk - you want to pick the active contact back up smoothly, with no resistance from the horse, rooting or head tossing, etc.
At a schooling show, and intro tests, I think you'll see other folks in AP or close contact saddles. If he moves better in that saddle, I'd use that saddle. Dressage is more about the horse's movement and obedience than it is about the tack.
Yes, wear gloves. I think tan breeches are fine at this level. While specific items aren't important, overall impression is. So have everything as spotlessly clean, neat and tidy as possible.
Hope that helps, and good luck.