As a support player, i'm used to supporting a team anyway i can, even when i'm playing a dps character, such as Kayle, and with this build i find it suitable to both sustain damage and assist the team whenever possible, i start off with a Mana Cyrstal to hold a good amount of mana when i am nuking with Reckoning / slowing targets for focusing, boots help me when i'm either fleeing or assisting, as i'm extremely aggressive early game, and passive late game. The 3 daggers are for good attack speed early on, your magic pen runes along with righteous fury and your innate should do a good amount of damage early on, spamming skills to allow your tear of the goddess to stack up early. Once you have nashor's tooth you should be switching lanes quite frequently to gank / roam accordingly to situations, grab red when you can while in this part of the game, assist a blue whenever you can, but you should not need it. Once you build your Manamune and Quinsoo's you will be getting your AD up to start attacking more tanky targets, early you should be only targeting squishies until you build these 2 key items. Once you get Bilgewater, you should find yourself playing a little more aggressively, using it as an active item. Use Reckoning to close and use Bilgewater to make sure they are slowed enough where you want them. Once you build Hextec, find yourself playing passively, only making necessary jumps when a more efficient person initiates. Hang back and back and shred them accordingly to victory.

I take Clairvoyance as a support skill, i am also a jungler, so it's easy to interpret enemy movements when they are hidden in the FOW (fog of war). If you want to take a more aggressive approach, take exhaust, or clarity, also, more passive players might want to explore more of a Utility Tree, as it is famous amongst US players