So that is my first guide. Tell me what u think, and i hope u like it.
The main idea of this guide is to focus on purchasing Last Whisperer, and using different runes as most Ashes do, that is no Armor Penetration but AD, or something else insted, but in this guide we go AD. U can of corse do what u want. But consider this guide as example how to use that idea..

And let me say right here, swiftnes, LW, IE, Phanthom, are my pick. AD runes are might not be the best but are bether than armorPen. Change seals and blue if you want(u probably do, maybe u will go cd seals, and mana reg seals, or i dont know, also think about movement speed quints, and consider att.speed), masteries are ok i think.

Skill levels are not set! just use ur sense of how game goes and what u feel u need.

Some things we have to know:
a)
formula: AD - AD * (armor -armorPen) / (100 + armor -armorPen)
b)
I dont say, "dont buy movmentSpeed Quint" or attSpeed or something, i say "dont buy armor Pen runes"
However most ashes go crayzy for arrmorPen, and that is not the best on my oppinion.
c)
Armor pen can't go below zero (runes, brutalizer,..)
Percentage armor pen can't go below zero (last whisperer,..)
Armor reduction can go below zero.. (stark's fervor, the black cleaver)
d)
I used top rated champs as opponent, for making examples:
asheas ad/mage carry or support (its only important for us how much armor they have)
Renekton as semmi tank or support
as tank
e)
I am bad at English, and i am sorry for that.

So at lvl 1, that means: (we did consider additional AD from masteries)
ArmorPen)
ArmorPen runes gives me around 20 armorPen.
I have 52 basic AD + 10AD form Doran's Blade and 20 ArmorPen.
If we have chance to be aggresive, and we have enemy with i dont know lets say 50 armor.
62AD - 62AD * (30/130) = 47.7 effectiveAD
AD)
AD runes give me 15 adition ad,
I have 52 basic AD + 15 from runes and 10 from dorans blade = 77AD
Lets face same 50 armor enemy.
77AD - 77AD * (50/150) = 51.33 effectiveAD

Summary)
So, for last-hitting minions AD is no-doubt bether.
And for being agressive too.
=>So LVL ONE no point to have armorPen.

Well lets take a look at ashe vs ashe. Where enemy ashe stands for enemy carry, so someone with low amount of armor.

Y = (77+2.85*x) - (77+2.85*x)*(x*3.4 + 9.3)/(x*3.4 + 9.3 + 100)
So that graf represents Damage delt by us(ashe) vs (ashe) at each lvl. Where we have AD runes, and no armorPen. (PS: all these graphs have actual damage delt on the left and lvl at the bottom)
(52+2.85*x) - (52+2.85*x)*(x*3.4 + 9.3 - 20)/(x*3.4 + 9.3 + 80)
Here we see the same thing, except that we changed the runes AD for armorPen
Well armorPen not good here(its 3/0 for AD runes alredy).

Well u say what about my IE and 80 dmg at lvl 10 + 20 armorPen, that have to be bether???
lets take a look then...
So here are ArmorPen runes and we have IE at lvl 10Now ad runes:
-we could think about having more money at that point,
-whole game should have some impact of bether early game(with ad runes)
-but lets just say, that we go for LastWhisperer hehe,
-on other hand, we did forget about crit strike of IE and 250% dmg of IE and so on.
-So IE cost €3830, thats like an Alfa Romeo 147 1.6 TS Progression (2001) and (100K km) on other hand we have LW for €2290 that is like Fiat Punto 1.9 D (2001) and over 150K km.
so 3830-2290=1540 difference, we can get Zeal for that money, and we have more than €300 in our pocket, that is like 3g Methamphetamine and few packs of cigarets.
But lets only buy LW so, u would spent like €1540 less.
Summary:

Ok lets do the same thing one more time: but lets do it faster...

1) lvl 1 Renekton-no items armor=15,2 base 15.2 armor + 10 for first item = 25,2
AD) 77 - 77*(25,2)/(125,2) = 62 actual damage done
AP) 52 - 52*(5,2)/(105,2) = 49 actual damage done

2) mid game renekton: 15,2 base armor + 12lvl*3,8 + lets say he have 10 for dorans and 68 for guardian angel = 138,8 armor.
AD) lets say: ashe have LW and another pickaxe = 77 base + 10 for doran + 12lvl*2.85 + 45 for LW and 25 for pickaxe = 191,2 and 40% armorPen (cost is 2290 + 975 = 3265)
=> 191 - 191 * (83)/(183) = 104 actual damage
AP) lets say we have IE = 80 damage and price is 3830, damage = 80 + 52 + 12lvl * 2,85 + 10 doran = 176,2 damage, we have 20 armorPen from runes
=> 176 - 176 * (119)/(219) = 80 actual damage

3) late game.. renekton have 176 armor
AD) 292 damage + 40% armor pen (we didnt count in bloodthirster bonus)
292 - 292 * (105)/(205) = 142 actual damage
AP) 232 damage + 20 (runes armorPen) + 20 Stark's Fervor + 45 (max from)The Black Cleaver
232 - 232 * (91)/191 = 122 actual damage

Look at the renekton at late game,..
u should understand alredy more armor that someone have => more valuable is LW

If we point out the obvious, 40% armorPen will be 28 armorPen vs ashe, or 68 armorPen vs renekton and up to 130 armorPen vs rammus.


Lets compare this guide with top rated ashe guide, ashe vs ashe, (if we beat ashe we will beat every one sooner than top rated ashe, that is becouse of the fact that more armor one have, more dammage we will do cuz of LW)

TopRatedAshe: 232 - 232 * (70-15-45-20)/(70-15-45-20+100) = 232 damage (it will not go under zero armor!, and that damage is only done in 3rd consecutive hit.
While at first hit that would be: 232 - 232 *(70-15-15-20)/(70-15-15-20+100) = 193 damage
And lets have another champ with 80 armor (so that topRatedAshe will not loose no armorPen)
she now deals 232 damaeg also.

MyAshe: (vs ashe)328 - 328 * (70-28)/(70-28+100) = 231 damage
(vs 80 armor) 328 - 328 * (80-32)/(80-32+100) = 221 (that is the biggest diference, where MyAshe is worst)
When we meet with champ of 90 or 100 or 300 armor, MyAshe is bether (wayBether)

The value of armorPen runes are over rated, among the ashe players. And LW is under rated. we dont gain enough early game from armorPen runes, we obvious cant compare them to LW late game. Mid game armorPen are good, but u can only get to mid game throug early game, so good early game will influence mid game (where armorPen runes will not help).

-If we think about AD runes, then we would see lienear influence on the game trough the game.
Something like red graph: its good on the begining, but its bether while we get more damage, and other get some armor.
-If we think about LW, well we dont need it at begining we are happy to have that extra 15 damage Then when we finaly can aford it, its like.."we could alredy have that 20 armorPen from runes", and that 900 feels like we throw it trough the window. But later its just the best.
Look at it as green line.
-the blue line would it be only ad runes without LW (but it should go down at liek 13 lvl->0.
-LW alone would just be line from bot to top. from left to right.GOOD
-early game
-late game


BAD
-mid game is a litle weaker as TopRatedAshe, if we consider, that we are fighting someone with low armor (but realy just a litle). If we fight someone with much armor, then LW will do its job, and MyAshe is bether.
-Early team fights are not what we want.