I've had the best luck with this build in my 100+ wins with Ashe so far. Going to try many many more this week.
Masteries
22/6/2 - Full offensive, 3 in increased armor, 3 in increased MR, 2 in improved ghost and teleport.
Runes
HP Quints, Armor Pen Marks, Crit Dmg everything else (contemplating an atk speed build in the future).
Summoner Spells
Ghost - Its just a given...amazing for escaping (better than flash for high tier players), king at chasing, and brilliant for getting in and out of fights firing off volley.
Item Build
Mana Gem - 2 HPots
Catalyst asap
Berserkers Greaves
The Brutalizer
**Build Banshees if ur getting focus fired**
You shouldnt be even close to 18 at this point, so continue to get more atk damage (pref IE).
Build Banshees if ur almost 18 (should be) else, blood thirster or cleaver.
Should be gg, else get whatever you didnt get previously.
I place a very high preference on attack damage when I play ashe. Why?
1)You are most likely going to be able to get one or 2 hits off before the enemy ur targeting retreats behind the remainder of the team.
2)Volley's damage increases with attack damage - its going to be your main source of damage while ur taking pot shots at the enemy team before you go in fighting.
ummm other than that i think the rest is self explanatory - if you need some clarification ask away, GL and HF with ashe ! She is one of the most heavily underestimated characters in teh game.