Ashe is a simple champion to play. Although to be effective with her you need to get a lot of farm.

Also ap ashe doesn't work her ult would have to be on a shorter cooldown.

Runes are pretty basic, Attack damage reds. (Armor penetration if you want a better late game)

You can go attack damage runes which will increase your damage in the beginning although I feel the armor penetration would help out more in the end.

Her masteries are basic ad masteries not much else that would benefit her really.

Boots don't matter, just berserker greaves is normal for adc's.
You want your first 2nd item to be infinity edge or bloodthirster.
You can replace your boots later on with phantom dancer for more crit/attack speed.

You can rush your E first which can gain you a little bit of more gold. And if you have twisted fate you wouldn't really need to do that/want to.

Your w/q should be primary to level, q to secure the kill and your w for extra damage.

Your R should be used to initiate teamfights/get someone who is running away, Don't waste your ult across the map unless you know you can get the hit on them. ex: recalling.

Build is okay for ranked play, although if you're getting countered, build to what you're getting countered by, such as if someone is ad, and is putting some damage on you, build maw.

Pros -
Ashe can do a lot of damage, and is also able to slow champions from getting away.
Doesn't need frozen mallet to slow.
Passive will allow her to do extra damage early
Able to counter ganks with e/show here people are.
Easy to kite as her the fact she has a slow.
Cons -
Somewhat squishy.
No get aways other than her stun or flash.
Some adc's are stronger.

Pick up smite. Pick up tought skin, volley, cloth/5pots.
Blue>Wolves>Wraiths>Golems>Red
Gank.

Her E is basically clairvoyance that doesn't last very long, but it can show where the enemy is and make ganks useless on you, it also gives you extra money upon getting farm.

Farming is okay, with her passive she can do some extra damage which I state above, but takes time to refresh. Needs damage to get farm easier.