Some newb Archer questions

So the elemental arrows, how exactly do they affect bows?
As in, do they increase the damage of snipe / cross fire / any other skills?
And then there are some bows which already have elements on them like the current Halloween event bow, which is wind element. So if I use this bow, will the element of the arrow be considered, or the bow?

Another thing, what are some good NPC/boss/mob drop gears for an archer, since I can't yet afford any actual player made gears.