Thank you for all the comments!

I prioritize Phage for the Health and the small amount of AD. In this stage of the game, I usually just keep farming.

And yes, there is a difference to pushing your lane and farming fast.
I like the 21/9/0, as said before, it's just about personal preference. Although, I sometimes faceroll with 0/9/21, I prefer 21/9/0

Max Bladesurge but don't prioritize a Sheen?

I agree that Irelia does need farm. For this reason I only use her if there is a solo lane available for her. She really excels in those situations. In my opinion she is one of if not the best mid champ. I agree with the items you have selected here just not the order. I like the philosopher stone first and boots of speed but I think sheen should be purchased before your lvl 2 boots. This will improve your burst damage early on when it's needed. I also max e very first for burst damage but I'll give your skill sequence a try. I like your Quints and I'm going to purchase those next. With speed in mind you should consider moving your masteries to something like 9/6/15 or 0/15/15. That way you get the speed increase from that as well. Since you build Irelia tanky she doesn't benefit from the offensive tree very much due to most of the skills granting % increases instead of a flat amount. I like the theory in this build and I'm excited to give it a try. I'll let you know how it works for me. Thanks.

I would get 2 in bladesurge if I'm having difficulties in my lane (usually 1v2 top) so I can last hit the caster minions after a turret hit with just a bladesurge, other then that I've gotten really used to lasthitting on Irelia so it's not a problem. Also if you kill the minions too fast it'll cause your lane to push and youll be able to farm less safely, wards don't always save you from over extending, unless its a very hesitant(bad) jungler gank.

You should steal the farm though, you need it like ****!

But the 21/9/0 is just personal preference, I like the cooldown reduction and the increased damage. Makes your burst so much better, and you can burst more frequently.

And Hiten does give you lanesustain, but so does harass in a way. Making them recall is really good. Not always netting a kill could still put you in a great advantage imo.

And, I really love lasthitting with "q", since with "q" you can last hit minions you otherwise couldn't last hit / farm so much faster.

You should try it, it works amazingly good :D

Item build looks extremely familiar to me for some reason. Decent build, but I would recommend going 0-9-21 or 0-21-9 since Irelia doesn't benefit from the offensive tree as say, an Ashe. I like to keep 1 in bladesurge and max hiten style and equilibrium strike first. Also you should activate hiten style before dashing since it applies on-hit effects. (If you need extra dmg for last hitting do this too)

edit* lol at the end where you say be nice, even though you say to steal farms in a duo lane :P