Summoners,
Here is my first guide on Mobafire. First of all, please excuse my approximative english.
I chose Leona as my first build because I really enjoyed the way you can play this OP champion!
For those who don't really know who's Leona, I'd say she's a mix between Sion, Jarvan IV and Amumu.
Let me explain that:
Her shield Eclipse is the same as Sion, besides it does not provide an extra armor but an augmentation of your magic and damage resistance. It will explode after 3 seconds, dealing a GREAT amount of damage. (I'll get back onto this)
Her Zenith Blade is like Amumu's skill, but even better! You'll deal damage toward all the enemies your Blade go through, and finally teleport to the last champion on your way.

I play here as a tank that can take a lot of damage, and also a great assist for the team (Aegis of the Legion + 2 stunts)
I hope you'll enjoy that short Build, as much as I did. I really won a lot of games playing Leona this way.

Since Leona is an AP/Tank, you'll need magic penetration. I've seen some people playing Leona with a full AP build, but Leona is NOT HERE TO DEAL A LOT OF DAMAGE. And that's one thing important to remember!
The Seals of Defense and Glyphs of Shielding are commonly used when playing a tank.

Yet again, the masteries 9/21/0 is the common skill tree for a tank.
Again, Leona is not a champion to choose when you want to deal big amounts of damage.
I've tried myself Leona as a full AP and a 21/9/0 masteries tree, it's not the way Leona was made for.

Early game, I start Leona just like I play Mordekaiser. She's quite low on mana and rely on the other in lane with you to finish enemies.
Kindlegem allows Leona's cooldown to be shorter, which make easier the track of ennemies. This item combined with Blue, and you're the greatest stunt of League of Legends.
Randuin is really helpful during teamfights. Any good tank will have Randuin in his hands actually.
Late game, depends on how the fight is going. If you have lots of AP in front, you should then get Force of nature instead of Frozen Heart.
Remember, you're not a killer, you're a GREAT help for your team during teamfights.

HERE WE ARE!

Just wait till level 2, when you get your Shield of Daybreak. When an enemy is near, just use Zenith Blade to get to him and stunt him.
When you get to have Eclipse, YOUR MAIN SKILL, here you'll be a pain in the ***.

Skill Sequence:

Active Eclipse
Use Zenith Blade to get to your enemy
Stunt him with Shield of Daybreak
Eclipse will explode
Use Solar Flare (on the whole enemy team or on enemies escaping)
Wait for CD

Your Ult is AMAZING in teamfights, but also when an enemy is escaping, or YOU are escaping (it can happens)
Always be sure to active Eclipse when ready

The main way you kill an enemy is that way. DON'T FORGET TO USE ECLIPSE BEFORE USING ZENITH BLADE TO GET TO THE ENEMY

Even though a champion is played differently by everyone, the way I play this Leona makes me win 7/10 games.
I hope you enjoyed that short build, short overview on how to play that OP champ (for now)

Summoners