Pros:
- Very strong damage output
- Great Support
- Very maneuverable (She moves very quickly due to her heal/speed buff)
- Great ability to not only carry but have a double carry (ability to sustain a 2nd carry due to invuln)

Cons:

- Slow early game
- Need to have a good farm
- Can't single handedly carry ( GREAT DUO QUEUE CHAMP! )

(Magic Penetration Marks): I run MPen marks on kayle because ALOT of her damage ends up being magic damage (from not only AP but madreds as well). These give you just a little bit of an edge going into the fight.
+ (Mana Regen Seals and Glyphs): I run flat mana regen because most of kayle's mana problems are early game. After you get your nashors the mana problems tend to subside. You could run Mana regen/level if you wanted, it makes a clear early game difference early.
(Flat HP Quintessences): Kayle is not a very tanky hero. Actually on the contrary, she is a 4bar mage early game unless you get some sort of HP, and since i chose to get the meki pendant as opposed to the dorans, i feel as though getting health quints is necessary. You could go dorans ring too if you'd like, its all preferential.

Starting Items: Start with either a meki pendant and 2 HP potions or a dorans ring, Then Follow the build as shown in the build order.

CORE ITEMS:
(Guinsoo's Rageblade): As of when you pick up this item, your damage hits a huge spike. This item is great because as it stacks AP, it stacks part of that as AD as well, making you hit much harder.
(Boots of Swiftness): The boots of swiftness are great on Kayle because when combined with her speed buff, they give you that edge you need to catch up and slow your target, then keep yourself in range as you whack away at them. You can also run Mercury Treads or Sorcerer's Shoes if you want. Sorcerers Shoes will give you an early 30 MPen, which is enough to get by most heroes base MR.
(Nashor's Tooth): This item is good for many reasons. 1, it provides more AP, which contributes to your overall damage output. 2, it provides attack speed, which contributes to your damage/second. 3, it gives you mana regen AND cooldown reduction, which just provides to your overall ability to support and attack.
(Banshee's Veil): The banshee's veil is in my opinion the best item for any mana using champ in the game (defensively). Any champ which has mana should get either this (or if they are melee, a randuins) at some point in the game. It will provide health, mana, and a very convenient shield. You can get this at any point that you feel you would need any more health (you are feeling squishy) but i tend to get it after my nashors tooth.
(Madred's Bloodrazor): When you pick up this item, you will notice another large spike in your damage output. This item can be replaced with the new + improved black cleaver, but i still much prefer the bloodrazor. It provides more attack speed, more damage, and a killer passive.... Literally. Great end game damage when people are starting to bulk up. Also, if you throw your Q on somebody, the % damage done by the bloodrazor is also amplified by the % that your Q will bonus. The madreds would proc for 4% of their HP then add (x)% of the damage of the madreds on top of it.
(Hexxtech Gunblade): The hexxtech gunblade (if you get this far) is the tip of the iceberg. At this point you will have a tremendous damage output, you would do ALOT more damage. The active and spell vamp (along with lifesteal) are also nice because your Righteous Fury will gain from both spell vamp and lifesteal (because it does magic AND physical damage).

The thing about kayle that confuses me is she doesn't really have a sequence. You have to get a feel for her before you go into fights and such. A good initiation is popping your Slow (Q) then using Righteous Fury (E) to shred their health as they run away. I would always save your ult for your carries (or yourself) when they get low, dont waste an ulti on a tank unless you HAVE to. Use your ult on the person who will do the most damage with it in the fight. Ex. if you have a twitch and an alistar in a fight. If the alistar is dying and 4 of them are in a row, when twitch pops out and they switch, use it on twitch, not alistar, because it is likely that he can kill more than the 1 that died in the fight, when alistar couldnt.

Use your W as not only a heal but a speed buff. If you see someone chasing the enemy, pop it on them for a huge speed bonus, use it on yourself to get away, etc.

Ghost: Ghost is a great skill for kayle. When combined with all of her speed it lets her keep up with any hero in the game (except for a rolling rammus... :( ... ). This will give you the ability to maneuver around their heroes or even run around to the back of the fight DURING a fight to get a kill on the carry, and worst case scenario, run away when you are low.

Flash: I use flash primarily as a positioning spell, you can exchange this for something like ignite but i like using flash to get myself in that PERFECT position to take out the carry, or again, pull epic flashes over walls to get away :)