Hello and welcome to my first ever made guide. I want to share with you my way on building Irelia. I've never lost even one ranked with her and I really love this way on building her. ^^
I'll discuss about what Runes, Masteries and Items I build for her and whats viable on her from my oppinion.

I go flat Armor pen/Attack speed Marks, flat Armor Seals, flat Magic Resistance per lvl Glyphs and flat HP Quints
I take the Armor Penetration for more damage with Bladesurge and Transcedent Blades OR I take flat Attack Speed for more True Damage and lane Sustain with Hiten Style.
Flat Armor Seals for more tankyness early game and a little end.
Flat Magic Resistance per lvl Glyphs for better tank mid - late game.
And last but not least I take flat HP quints for better sustain early and a little more dmg with my atmas(Not important at all).

I think that Armor pen or Attack speed is best for Marks and I think that Magic resistance per lvl is best for Glyphs
You could use Dodge on seals, but I think that you can not really rely on them so I got with Armor instead.
You could use Armor Pen Quints if you want more damage or you could take Hp reg for even better sustain, but I think that the hp ones is good enough.

I take 0/21/9 in Masteries. 21 in defensive because the extra tankyness you recive from it is really great, you get more CC Reduction and more Hp Reg which is really great.
Take the other 9 points in Utility, this will give you less Cooldown on Flash and Teleport, less deathtime (10% which is really good) and some extra Movement speed.

I start of with a Regrowth Pendant and one Health Potion. My first time back I alway try to grab a Philosopher's stone and a pair of Boots and/or Heart of Gold, deppends how good your farm goes and who you're against in top. When I got my two gp/10 items and Boots I try to get a Phage for more Damage with Q and R, some HP and the really good slow, I dont know how many times the Phage have helped me to get a kill. Now you should try to get your Mercury's Treads. After a while I'll get Atma's Impaler for obvious reasons, Dmg, Armor and Crit.
I build my Phage into a Trinity Force, sell Philosopher's stone and buy Warmog's Armor and then a Randuin's Omen, but if you're against a heavy ap team then consider Force of Nature instead of Randuin's Omen.
If you die alot you can just buy a Guardian Angel quickly.

Starting items: Regrowth Pendant and one Health Potion
Early game: Philosopher's stone, Heart of Gold and Boots
Core: Guardian Angel, Atma's Impaler, Trinity Force and Warmog's Armor
Situational High AD: Randuin's Omen Frozen Heart
Situational High AP: Force of Nature Banshee's Veil

I always max Hiten Style(W) first for better sustain in lane and really nice True Damage.
Then I max Equilibrium Strike(E) for the nice damage and the slow/stun and I put a point in Transcedent Blade(R) whenever I can.
I max Bladesurge Q last cause I dont find it really great, it's ok when you got Sheen but I mostly use it as a close-gaping ability.
You could max Equilibrium Strike before Hiten Style if you want,cause it's a better nuke and slow but I think that Hiten Style is better cause it has True damage AND gives you HP on each attack which is really good in both laning phase and in teamfights.

I take the standard solo top Summoner Spells cause I find Teleport really useful, you can teleport to a ward at Dragon and turn a teamfight around or you can teleport gank, or you can teleport to defend a tower and some more stuff.
I take flash for obvious reasons, you can flash from a gank, a tough situation or flash after another who've flashed away from you.

I really love Flash so thats why I take it over Ghost but after the Flash nerf I think that Ghost can be a little bit more usefull in some situations.
You could also take Ignite or Exhaust instead of Teleport.

So, this is how I build my Irelia. I really hope you enjoyed reading it and please leave me some comments and vote, and if you can please tell your friends who plays LoL about this guide. I would really love if we could discuss the masteries and the items
I've got 1 Penta kill and 4 Quadra kills with this build so far. So I wish you all good luck and now go out there and kick some ***es with the coolest char in the game! >8D Thats all from me, bye and thx for reading. ^^