Needs no introduction.

Pros-

Great support damage
Makes squishies cry
All in one package:
dash (q), heal (w and ult),
range (ult), on-demand stun/slow (e)

Cons-

To meet full potential, relies on teamwork
Can be tough against champions that can spam:
e.g. Cassiopeia

This masteries setup is generally good for all DPS users, but I chose it for Irelia for specific reasons.
Though there are other masteries setups (defense/utility route), the offensive route is much more beneficial, especially when the Irelia I am building is 'offensive'.

The downside with Irelia is that her base damage at start is quite low compared to other melee champions and that +3 damage makes up a great deal for creep killing and dealing early game damage. Apart from that, the other branches from the offensive tree compliments other parts of my build with the additional armor penetration, critical chance/damage, and attack speed.

As many have argued before, what runes should I get?
Armor penetration, critical chance/damage, attack damage, or attack speed?

In summary, runes are set up as an additional source to benefit early game or late game; pure stats runes or stats by level runes.

Out of these arguments, what I figured was best for DPS is, as most would suspect, armor penetration. Armor penetration benefits early game by a lot with champions below 100 armor because it reduces enemy champion's damage reduction by a lot, especially with squishies or low armored champions. So by having armor penetration, it allows you to deal more of
your damage early game. As a plus, the 'offensive' masteries gives an additional 6 armor penetration.

Now, just because armor penetration was declared as the chosen source of damage output, it does not mean other sources are inadequate. In actuality, since armor penetration only works well with champions below 100 armor, that would mean it would not be as beneficial with champions with a lot of armor, which is something to note in purchasing items.

Apart from physical attack runes, I chose magic resist runes for glyph because if you were to consider runes-by-cost, glyphs provides more magic resist. And I chose set magic resist runes because my purpose of magic resist runes is to provide me enough survival vs ability power users until I can deal immense amount of damage output so that they can't kill me.

For seal runes, I chose hp per level because it provides an absurd amount of hp by level 18, 175 by level 18, which fills in a part of its role for Irelia's survival hp-wise.

When it comes down to summoner spells, it really depends on your play style. For every champion, there are many variations in which summoner spells can benefit the user.

For DPS-type champions, combination of summoner spells may include:

Ghost and Flash
Ghost and Ignite
Flash and Ignite
Ghost and Exhaust
Flash and Exhaust

After experimenting with these variations, I found Ghost and Ignite to be fitting for Irelia.

Between the two movement summoner spells, Ghost and Flash, Flash allows Irelia to make a surprise attack or better escape mechanism, while Ghost allows Irelia to chase and constantly attack with Hiten Style (w active) or run away faster.

Between the two support summoner spells, Exhaust and Ignite, Exhaust slows and reduces incoming damage, while Ignite deals true damage over time and reduces enemy healing and regeneration.

Looking at the functions of these summoner spells, Ghost and Ignite would provide Irelia with full 'offensive' capabilities.

Starting item... is probably one of the essential part of the game.

The goal of my item composition is to get gold as fast and safe as possible.
By rushing for Madred's Razors, it will allow Irelia to get faster creep kills (gold) by chance. And by rushing for Wriggle's Lantern, it will allow Irelia to utilize its ward active to acquire vision so that you can play safer so that you can farm.

Now before you get these items, what should you get first...

Like any jungler who goes for Madred's Razor, Cloth Armor and hp potions suits best. The only difference is that I chose to get 3 hp potions rather than the usual 5 because I am confident enough that while laning, I can survive with just the 3 to buy Madred's Razor a bit faster.

After getting Wriggle's Lantern, farming should be a breeze as junglers do. The item to get after Wriggle's Lantern should be Sheen, primarily because of its passive to deal 100% bonus damage after using an ability. Especially for Irelia, her dash (q) ability consecutively activates the Sheen's ability, dealing that burst damage.

After getting Sheen, most Irelia players I've seen rushes for Trinity Force thinking it is a must and that after getting Trinity Force, you'd be unstoppable, but I differ. By calculations and cost-wise, the benefit of Trinity Force's 150% bonus damage does not take effect until around 200 damage, which is why I choose to get a B.F. Sword then Phage then Trinity Force. By getting B.F. Sword first, your physical damage boosts your dash (q) damage and Sheen's ability. This goes for other DPS champions as well...

After completion of this item build, depending on where you and your team is at in the game shall you choose what other items to get.
If your opposing team is dominating, obviously, get defensive items, such as Banshee's Veil.
If your team is dominating... it doesn't really matter how you finish your B.F. sword, though I favor the critical damage route, with Infinity Edge, then Phantom Dancer.

Before you start a game, you have the decision on whether to jungle or to lane.
In my opinion, jungling is absurd with Irelia since her jungling capability compared to other junglers are inadequate for getting gold and advancing to help gank lanes. Laning, on the other hand, can either be easy or difficult depending on who you are against.

It is best if you can solo lane vs a champion that you are good against so that you can farm items faster. But I suggest not to duo lane aka 1v2 lane.

In the early game, you should try to last hit creeps to acquire enough gold for Madred's Razor, and after you get Madred's Razor, its ability should allow you to farm much more easily without worrying too much about last hitting.

During this process, a way for Irelia to last hit creeps is by utilizing her dash (q) ability where if you kill a unit using the ability you replenish half of its mana cost and allows you to reuse it consecutively.

For the starting ability, I suggest Bladesurge or Equilibrium Strike, based on who you are laning against.
If facing a melee champion, Equilibrium Strike is my choice since Bladesurge is mostly used for Irelia's limited range, and farming should not be too difficult.
If facing a ranged champion, Bladesurge is my choice since they would probably harass (or try to attack) you, so Bladesurge allows you to at least make an effort to farm.

The goal of this build is to max Equilibrium Strike asap. The reason is because Equilibrium Strike is Irelia's main source of damage in the early game. In comparison with Bladesurge's and Hiten Style's active's damage output, it is not reasonably effective as Equilibrium Strike's one-hit damage. Not only that, with Equilibrium Strike's ability, it can stun/slow the opponent as its level grows.

The secondary and main source of ability damage after early game is Hiten Style's active. With true damage, it makes any champion feel weak.

Bladesurge at level 1 is sufficient for the entire game until you max out everything else because of its ability to reuse it if you were to kill a unit with that ability.

As already been mentioned in Cons, for Irelia to reach full potential she requires teamwork. In addition to that, like any other champion, smart gameplay is necessary for survival and to pursue your goals.

What I mean by smart gameplay is how to approach different situations.

During laning phase, side lanes is suggested over middle lane mainly because bushes are your friends. Irelia cannot recklessly approach another champion since her damage output is not great until she has accomplished farming. By using the bushes to approach enemy champion(s) you can try to prevent as much incoming damage and also deal damage as much as possible using Equilibrium Strike or Bladesurge.

During teamwork/gank phase, Irelia still cannot recklessly approach the opposing team. It is obvious that the enemy would want to kill off the DPS or burst damage champions in one go. So, waiting for a tank or an initiator is an obvious approach. When a team fight has been initiated, Irelia, like any other dashers, should target enemy damage dealers.


And now for techniques:

My set combo for Irelia is Q > E > W (dash > stun/slow > damage)
This combo is my preferred approach since it allows Irelia to deal that burst damage people fear. The only time I would change this combo is if I were to conserve mana and if the enemy I am targetting has a spell block ability. Something to note is that if the target enemy has a spell block ability and you were to use Bladesurge, it would not only block its damage but it would also block Sheen's ability. To prevent this, sacrificing Equilibrium Strike is reasonable so that it breaks the spell block and allows you to deal Sheen's ability damage.

Two things to consider are the functions of Equilibrium Strike and Transcendent Blades:

Equilibrium Strike can stun/slow the target depending on your hp % compared with the target's hp %, not hp difference. A way to see this is by looking at yours and the target's hp bar, and you can see the notable difference and utilize Equilibrium Strike's ability to stun as much as possible.

Transcendent Blades is a skill shot which has 4 shots that pierces in a line, healing 20% of total damage. Note that it pierces in a line, so to maximize its healing ability, you should try to pierce as many units as possible so that it can deal maximum damage hence maximum heal.

Knowing these two functions can allow you to survive and/or make a kill.
Since Equilibrium Strike's ability disable depends on hp %, the ideal disable is the stun. So if you take note of your health and your target's health, you can stun them constantly. Another thing to note is that when you and your target both have full hp, that's an automatic stun.
Transcendant Blades is the only range Irelia has apart from Bladesurge's dash, so using this skill wisely is somewhat important. When Transcendant Blades is active, it provides a moderate duration for you to use it decisively. With that time, you can either use it to heal yourself, clear waves of creep, pierce/splash lined up enemy team, or finish of a kill.

Lastly, the infamous technique by Irelia is her double-triple dash combo.
We've seen Akali do it. We've seen Renekton do it. But can Irelia do it? Yes. When you get use to Irelia's Bladesurge ability, since it replenishes half its cost and allows you to reuse it IF you kill a target unit, you can use it consecutively as long as that happens and have mana.

What's more to say?
Irelia is one hellofa champion.
If taken to another level, she can dominate almost any champion.


Good luck with Irelia and hope you learned much from this guide.

P.S. If you want me to post pictures to make it all nice and fancy, I can. This build/guide is ideally for key concepts to consider with Irelia.

Feel free to leave any comments or questions.