Just started to play Irelia a few days ago, and I found out several build fit her.
Well, first I go devourer, then boots (CDR, swiftness or Attk speed), then I may buy : spirit visage, dead man's plate, sunfire, banshee's, guardian angel, Botrk, etc...
I don't what's the optimal build for her.
Succubús GF1 votesThat is actually a super good build for her. I also hear trinity is good on her, but I have never tried it.
SnugglePuggle941 votesIt's her main item....
EndlessSorcerer1 votesYou really should.
Trinity Force has been her core item pretty much since she was released. Many games, it would be her sole damage item and it would still let her assassinate squishies.
TheTarians1 votesMy usual Top Lane build ATM is: 
or 
(Depending on if they have more AD or AP) 
and then just straight tank after that.
When going jungle, I basically just throw a devourer in there.
EndlessSorcerer1 votesWhile these may not be the best builds, they should work fairly well to get your started. Obviously, you will probably have to adapt your build depending on the game.
Top Lane:
[Split-pusher/Duelist]
[Diving "Assassin"]
Jungle:
General, you want a mixture of attack speed, resistances, CDR, and Spellblade in your final build. You can get them through any source you like, but those are my preferred options.
If you are wondering why Rageblade is being built, that is because:
Generally, Probuilds.net and Champion.gg are useful for finding builds when you are first learning a champion.
SnugglePuggle941 votesWhether as jungle or top, unless you are getting shit faced, you always rush TF as your first item. That's her main power spike. So if jungle, after you finish your smite item and boots, get your TF. Then for me it's a matter of what I think I need, whether more damage or safety. Also, guinsoo's is hilarious on her.
darkmatchwaldo1 votes
is my standard build.
Victurn Up1 votesHm I think the red jungler item is waaaay better on her, as recommanded. Her W already deals raw damages, so wil the smite on champs.
darkmatchwaldo1 votesProbably i just like the Tracker's Knife on every jungler, i think vision is more important than anything else. Especially with the removal of stealth wards. It just fits my style a little better, i like to counterjungle and drop wards in their jungle to keep an eye on things.