Not Updated For Current Season
The masteries shown here are not yet updated for the current season, the guide author needs to set up the new masteries. As such, they will be different than the masteries you see in-game.
*** This build is not for 3v3 matches! ***
The Quints and points in the Utility tree are pretty variable for this build. I like the dodge quints for that little bit of survivability (and I have them anyways), and I prefer to level quickly and keep my neutral buffs for as long as possible. However, this build can also work well with points in the Def tree and other Quints (like spell pen, cooldown reduction, movement speed).
This build is a nice build that requires some patience and farmability to play. Around level 4 and 5 you should start hitting them hard with reckoning, and from level 3 forward you should be farming hard with Righteous Fury (although ideally you can last hit without it and save some mana). Pop smite whenever it's up to grab some extra cash, and Clarity lets you pop all your skills pretty continuously early on. Also don't forget to pick up healing pots with your Meki Pendant so that you can focus heals on your lane buddy.
***NOTE: It's really not worth getting Mejai's early if your team isn't getting kills, because early on you're not in a position to really get them on your own. As a support hero, it's much easier for Kayle to get 20 assists than it is to get 10 kills. You can even grab an assist for healing an Ally in battle
The most important thing you can do with this build in the early game is prepare for the late game. Grab some stacks and make some cash so now you're really ready to kick some ***. Smite is great for keeping the Golem buff, along with the other neutral buffs, and you can also use it to wreck Heimer's cannons and other hero pets. In battles I would say to pop Righteous Fury early and get that first Sheen hit off, then try to throw your reckoning down to maximize your DPS output (and heal like crazy to keep the sheen coming). Otherwise by this point you should be a healing saving damage machine. Your passive takes your large Ability Power and converts some of it to Damage, and your Righteous Fury does the same make your regular attack a rather potent combination of spell and attack damage. Your Reckoning should be awesome, assuming you have some spell penetration in your runes, and some extra from your boots as well, and you're heal should be much more useful with all the ability power you have lying around. The only thing you should really have to do at this point is not get too cocky, and try to keep intervention on whoever's getting hit the hardest. Remember, you're still pretty squishy.
Hope you guys find this guide helpful. Keep in mind this guide won't get you kills, it will get you wins (and a lot of assists).