Hello
Before starting i'd like to say that i'm not good at writing guides (this is also my first one), and i'm not too good in english either. So try to look over that

PROS

-Nice heals who provide run speed
-Immunity to damage
-High mobility
-Amplifies the damage done by your team on targets when u attack them
-Can turn the tide of a teamfight
-Amazingly fun to see how you keep your team from dying while being untargettable (very long range support)
-...

Kayle doesn't need much since he has pretty good stats itself. I only felt like i wanted little more mana regen, so thats why those replenishment seals. Having those AP runes is not really a must, but it helps your early game alot. you'll be doing amazing damage at high range... good to assist the carry on your lane with some damage...

For items i wanted to max out my cooldown reduction, because thats the only downside on Kayle i think. His heal has a little too much cooldown. But by lategame, with some CR its just fine. and besides that, the armor from omen, and the hp you get from items makes you hard to kill. (if you also position yourself well, you wont be killed at all)
Be sure to keep one free bagspace for warding, because thats extremely important. (if ya dunno how to ward, check this site, there are some amazing warding guides :))

As summoner spells i take flash, and heal.
flash is just to get out of those tricky situations that would otherwise kill you, and heal, well, with the new buff it got its too OP to not have it.
teamfights are like this: either your team rules and you wont be needed, or your team gets his *** kicked, give immunity to the carry thats getting targetted, get in range and use summoner spell heal and than some heals to help your team get away/chase them down. and before you notice you made your team win the teamfight. so heal IS important

This was my first guide, i know things may not be explained well, or abit hard to understand, sorry for that. I hope that you atleast learn anything from it, try it, and have some fun with it. Feel free to comment if you do not agree with something. I will evaluate it and if needed change it.