Leona is probably the best support in the game. She is in the top tier of supports due to her high CC(maybe the best CC champion in the game). So here is my build for her hope you guys like it and rate it.

So in this guide I put down Ignite/Flash as summoner spells and here is why:
-Ignite is good on Leona because it gives a lot of kill pressure in the lane.
-Exhaust take it only when you play versus really mobile champions such as Jynx.
-Flash is needed in any situation because Leona doesn't have any escape.

So as you see i put Mercury's threads with Distortion ill tell you more about that in the Team Work chapter. So if they have a strong early game support like Thresh always start with a Doran shield and don't fight until level 3 NEVER!
And maybe instead of Sunfire cape you can get the Locket of Solari if you want to soak up some damage from the enemy team but its your choice I like Sunfire more. And don't upgrade the Sightstone because you can put only 3 wards down so its just spending money. At late game you can maybe sell the Face of the Mountain and buy a Iceborn.
Boots are situational if the have a strong Magic damage and CC you buy Mercury's or you can buy Mobile boors for faster rotations and roam.

As long as you have the relic item last hit the cannon minions to split the gold with the ADC and to heal him at the same time.

So in team fights you want to be in the front line and as soon as you can land a multiple R on them its good. The Distortion enchantment is needed for the Flash/R initiation witch is very useful and the enchantment gives a lot of CDR on summoner spells and you have flash in every ~3 minutes(instead of 5)

This is a easy one you just post level 6 E W Q and after 6 initiate with R and then go standard E W Q.