I want to remember that's just a Dominion guide, yeah of course the build is suitable for classic game too, but don't expect to make an huge number of kills, because Leona is more like an huge cube of cast-iron that walk around the map scaring the enemies with her double stun.
I've to admit that I bought Leona cause was since the start of my LoL, the champio I wanted more then everybody.
At the start I had huge issues how to menage the Zenith Blade and the stun from Shield of Daybreak, but when you get inside the view of the perfect range for ZB you wont fail anymore to stun none, as well we have to say you must active Eclipse just a second before, jump on your target.
About her ultimate Solar Flare, i think it's really op if you cast it just on the cluster of the enemies champs closer the enemy's turret
Basically the skill seguence will be Solar Flare --> Eclipse --> Zenith Blade --> Shield of daybreak.

Basically Leona skills are so powerfull and different in base the circumstance, I admit i saved my *** several times by cicling SoD and SF then again SoD, stunning who chase me till reach the closer friendly tower where I'm covered from possible allied too.
Just to add about the objects built, in base if your enemy are more AP then AD just start with the two christal of the Cathalyst then the Heart of gold. As well if you prefer instead of Aegis of the legion, you can make the Guardian Angel, but i prefer the first one for give a nice buff at the allies closer.

Thank you for chose my build, I hope you'll find it very usefull and will enjoy the tank queen^^

Pros:
- Already resistant at the start.
- Unkillable on the end of the game
- Double stun double fun :)

Cons:
- Ridiculs damage
- You meight steal some kills