*Please Note that the "Step By Step" section is OPTIONAL the Core + Options part well its self explanatory.



Step By Step:

Start: Boots + Health Potionx3

Once you got yourself 1,850 or more gold get yourself Madred's Razors + Mercury's Treads.
Next once you have about 2,250 gold grab yourself Wriggle's Lantern + B.F. Sword or if you don't have enough Dagger.
Farm minions and get yourself some kills/assists until you got about 1,635 gold then grab yourself Black Cleaver and Dagger. Or if you got Dagger instead of B.F. Sword 2,865 gold.
If you can't tell what your next item is, well don't bother to guess because its Zeal which is about 775 gold if you got yourself the Dagger.
Since you got all that why not some more damage? Well your wish has been granted get your self Last Whisper for about 2,290 gold or if you want to go with an even more damage output if you think the game will last a long time grab yourself Infinity Edge for 3,830 gold. Either of the two are good its all into preference, personally I'd get a Infinity Edge, but the Last Whisper offers a good perk + about 40 damage!
How about a little recap on what you should have shall we?

Mercury's Treads + Wriggle's Lantern + Black Cleaver + Zeal + Infinity Edge or Last Whisper

Now, as you can guess your going to want to finish off that nasty ol' Zeal into a Big Bad Phantom Dancer for about 1,650 the same price as B.F. Sword if i might point out, though don't get it.
Aah the final stretch of the build, This part is purely based off of your opponents. If you got a lot of Casters/AP Champs on the other team you might wanna think about investing into Banshee's Veil for some spell cancellation + magic resist and some extra HP n Mana which is 2,715 gold, or maybe a Wit's End for that extra little attack speed and some passive magic damage which is 2,150 gold.
A couple of other options are for going against Casters/AP Champs:

- Spirit Visage Offers Magic Resist, Health + some amazing passives: 10% CDR + 15% Healing and Regeneration effects on self. Tip: This will go well with your passive in case you wanna grab it early game, all your choice.
*Price - 1,550

- Guardian Angel Gives Armor and Magic Resist along with an extra life!
*Price - 2,600

Now in the event that they have a lot of AD Champs these options are also good:

- Guardian Angel Gives Armor and Magic Resist along with an extra life!
*Price - 2,600

- Thornmail Gives massive armor bonus + deals 30% of Basic Attack Damage back as Magic Damage
*Price - 2,000

- Randuin's Omen Gives you some good armor, a little bit of health, and a decent amount of health regen. Also gives you 5% CDR, 20% chance that enemies who hit you with Basic Attacks will slow their Movement + Attack speed by 35% for 3 seconds. If you activate it, it slows movement and attack speeds of surrounding enemies by 35% for 2 seconds + 0.5 seconds for each combined 100 armor and magic resist you have.
*Price - 3,075

- Frozen Heart Gives as much armor as Thornmail -1 and 500 Mana. Gives 20% CDR and Reduces the attack speed of enemies close to you by 20%
*Price - 3,075

Core + Options

Core:
- Mercury's Treds 1,200 Gold

- Wriggle's Lantern 1,600 Gold

- Black Cleaver 2,865 Gold

Options:

ATK Damage:
- Infinity Edge 80 ATK Damage, 25% Crit. Chance, Critical Strikes deal 250% instead of 200%
*Price 3,830

- Last Whisper 40 ATK Damage, 40% Armor Penetration
*Price 2,290

- Youmuu's Ghostblade 30 ATK Damage, 15% Crit. Chance, 15% CDR, 20% Armor Penetration.
Active: Grants 20% Movement Speed + 50% ATK Speed for 4 seconds, Basic Melee attacks increase duration by 2 seconds. (Max of 8 seconds)
*Price 2,687

ATK Speed:
- Phantom Dancer 55% ATK Speed, 30% Crit. Chance, 15% Movement Speed
*Price 2,845

- Malady 25 AP, 50% ATK Speed, Basic Attacks deal 20 bonus magic damage and reduce targets magic resist by 6 for 8 seconds (Effects stack up to 4 times)
*Price 1,825

- Nashor's Tooth 50% ATK Speed, 65 AP, 10 Mana Regen. per 5 seconds, 25% CDR
*Price 2,885

- Madred's Bloodrazor 40 ATK Damage, 40% ATK Speed, 25 Armor, Basic Attacks deal bonus magic damage equal to 2.5% of targets max health.
*Price 3,800
**In Replacement of Wriggle's Lantern; Also get some Life Steal if this is bought.

- Wit's End 40% ATK Speed, 30 Magic Resist, Basic Attacks deal 42 and extra magic damage and increase your Magic Resist by 5 for 5 seconds.(Effects stack up to 4 times)
*Price 2,150

- Zeke's Herald 250 Health, 15% CDR, Gives nearby allies(and you) 12% Life steal and 20% ATK Speed
*Price 2,145

Armor/Magic Resist/Health:
- Spirit Visage 30 Magic Resist, 250 Health, 10% CDR, + 15% Healing and Regeneration effects on self.
*Price - 1,550
**Tip: This will go well with your passive in case you wanna grab it early game, all your choice.

- Guardian Angel 68 Armor, 38 Magic Resist, Revives Champion upon death(At spot where u died) with 750 Health and 375 Mana(5 Min CDR)
*Price - 2,600

- Thornmail 100 Armor, deals 30% of Basic Attack Damage back as Magic Damage.
*Price - 2,000

- Randuin's Omen 75 armor, 350 Health, 25 Health regeneration, 5% CDR, 20% chance that enemies who hit you with Basic Attacks will slow their Movement + Attack speed by 35% for 3 seconds.
Active: It slows Movement and Attack Speeds of surrounding enemies by 35% for 2 seconds + 0.5 seconds for each combined 100 armor and magic resist you have.
*Price - 3,075

- Frozen Heart 99 Armor, 500 Mana, 20% CDR, Reduces the attack speed of enemies close to you by 20%
*Price - 3,075

- Banshee's Veil 375 Health, 375 Mana, 50 Magic Resist, You gain a Spell Shield: Blocks the first incoming enemy ability(45 second CD)
*Price - 2,715

- Locket of the Iron Solari 300 Health, 35 Armor, Allies(and you) gain 15 Health Regeneration.
Active: Shields you and nearby allies for 5 seconds absorbing, 50 + 10 Per Level, Damage(60 second CD).
*Price - 2,125

- Atma's Impaler 45 Armor, 18% Crit. Chance, You gain ATK Damage equal to 2% of your max health.
*Price 2,355

For your Runes I suggest the following:
Marks - Greater Mark of Attack Damage
Seals - Greater Seal of Armor
Glyphs - Greater Glyph of Magic Resist
Quints - Greater Quintessence of Attack Damage

For your Masteries I suggest 21-0-9:



Or 21-9-0:

our main Priority is your "W" Burst of Speed Get a level in that whenever possible, maxing out at level 9
At level 2 get Lunge and at 3 Riposte alternating between these two when you cant upgrade your Burst of Speed and of course get Blade Waltz at 6/11/16.

So your spell Priority is like this:

Blade Waltz - Burst of Speed - Lunge & Riposte

**Alternatives in Descending Order

Preferred:

- Exhaust

- Ignite

Alternatives:

- Ghost

- Flash

- Smite
*For Junglering

- Surge

- Teleport

- Promote