Irelia is a really fun champion to play combining perfectly really cool mechanics to fit every game style as well as great appearance in the game. She is a mid - late game champ which most of the times will get out laned from every other champion but if managed correctly even if back in levels can have a huge impact on the game from splitpushing turrets to effectively 1 v 5, counterjungling or even being a very mobile tank that can engage and disengage easily.

Pros:
Incredible CS Potential
A lot of Sustain
Great Mechanics
Easy Engage

Cons:
Moderate Disengaging Potential
Early Game Sucks
Can Get Poked

After Getting Your Tri Force:
You can oneshot mage minions. Try to stun the enemy then open w and autoattack him. if he flashes or try to get away q a mage minion to get closer and do one or two more basic atacks then wait for trinity (1 sec) and q on the enemy and aa. Use the reset at your advantage. Try to have q always up.

Q Lock Instaburst
If enemy flashes with no hp left and your q cant reach him either reset it on a minion to get closer or q on the enemy and flash towards him. You can travel an insane length and hit him.

Stun under turret
If you cannot kill someone hire the turret to kill him. Bait him in the turret range then stun him and the q away or aa him. Easy early kill.