Hey guys!:)
In this guide I'll try to show you, how to play Leona ( normally played as support / tank ) as an APC ( Ability Power Carry ).
The most of you 'll think "OH GOD... WHY?!" - yes... a good question... the answer is : Fun.
A game like LoL should make fun... but fun is not the only "pro" for Leona. ( More later )
My English isn't the best, so don't expect to much! ;)
Yeeeees... let's go! :)

This are the "main" items, the core , you shoud buy them in every game!

~ AP = Damage
Damage = Kills
Kills = Becoming fed
Becoming fed = op - should i say more?!:)
~ AP + MR + Aura. The Aura is OP for your W :) The MR allows you to survive at your lane!

~ AP + Life + every spell slows. " Why ? " - Thanks to Eclipse it's just really nice , 'cause of a great slow. Enemies can escape really difficult if you buy this!
--- Better take an other item, Lich Bane works not really good , 'cause of the high cd's.
Thanks to astrolia !

This is a long part in this guide, 'cause nearly every AP item is nice with Leona. And that's the problem! Try some of them, and if you find your right items, you'll win your lane... and can carry the game ;)

~ Armor + AP + Active. It's nice, if you are early target, the active can save you really often! The armor is just good against AD-Champs ( Attack Damage Champions ) ,if the enemies have only AP-Champs, don't take it! ( exception : The enemies have Karthus - it counters his ulty hard! :) )

Deahtfire Grasp ~ AP + burst damage - it 's nice for damage - and great against tanks! :)

~ AP + Life + Mana. Nice to make you more tanky. Feel free to buy!

~ Mana + Manareg + AP. I think, this item is NOT so useful - you have to high cd's for it! But ... try it!

~ AP + Magicpenetration. Great against MR stack. A must have against an enemy like Galio

~ Too risky. You can try it... but ... it's REALLY RISKY !

~ Really much people think this items is "useless" or just "bad". But no - it isn't. Nice early game item - it makes you able to win your lane easily!

~ In combination with your Lich Bane and your Shield of Daybreak it's really strong!

~ some AP + Tenacity - Just if the enemies have a lot cc's.

----

~ This Item CAN be good and is a great combination with your Shield of Daybreak - but keep in mind : your cd's are high!:/

There is one Item, that i forgot :

~ This Item is useful to have some less cd's, still nice ap + mana reg boost. So you can buy Kage's Lucky Pick in early game to get more gold. With the active you can counter some Champs ... or let's say , some abilities.
Examples :
- Soraka 's heal abilities
- Volibear 's passive ( The Relentless Storm )
- Dr. Mundo 's high life regeneration

Some items are still useful,although don't give you AP.

~ Armor + Mr + Revive! Nice to turn a fight, if you are an early target.

~ Armor + Mana + Slow Aura. Allows you to survive longer and case / escape better!

~ A great Item against an AD-Team! Champions like Yi, Gangplank ( and nearly every ADC ) are countered by this.

~ MR + life + mana + spell shield. Nice against powerful mages!

This is the ... "difficult" part of Leona , played as APC.
There are a lot of boots she can take, choose them with a short time of thinking ;)

~ This boots makes you able to chase and escape better. I think, you don't need it. For chasing you have Zenith Blade. For escaping... a lot of stuns!

~ Your High cd's are a hard problem! Feel free to buy, to decrease this deadly cd's!

~ MR + Tenacity. You can survive longer against AP-Champs and get lower cc's. - Just buy it, if these are problems for you!

~ Armor + lower damage by auto attack. Mhm:/ Just take it if they have REALLY high ad damage!

~ Magiclepenetration - take it if you want build FULL ON DAMAGE !!! ;)

Wuhu... the summoner spells. This is easy to say...

- THIS IS A MUST HAVE! :o


- THIS NORMALLY ,TOO! :o


Other possibilities are :

- No one can escape from you! x)

- Makes escaping and hunting more easy. But... i think Flash is still better.

- Just a Heal. Mhm. It's possible ,too. ( I 'll never pick it... )

- You come back to your lane more easy and can gank other lanes. Nice, but NO must have!!!

Soo, now i'll tell you how to skill, and why to skill like this. Some "gameplay-tips" are included.

Ok , you have to Skill like this : E-Q-W-W-W-R-W-Q-W-Q-R-Q-Q-E-E-R-E-E.
" Why Zenith Blade first? " - It allows you a short stun, range attack, jump to an enemy-champ and the main reason for taking this : you can pull for your jungle!

" Why full skill Eclipse first? " - You can easily clear minion-waves with it and get less damage. The "wave damage" is really good and with your E it 's easy to damage an enemy with it.

" Why full skill Shield of Daybreak then? " - In combination with Sheen or Lich Bane it's really strong. With your E you can easily target an enemy.

It 's difficult to get minion-kills (last hits) with Leona at mid. An alternative would be the top lane, but no - this is a mid guide!x(

With Zenith Blade you can get some last hits - BUT CARE :
Don't target an enemy-champ!

You can win your lane easy, if you have "the right enemy".
(more later ...)

" How should i kill a champ in the early game? " - You can't do anything to lvl 3. Sounds sad, but at lvl 3 your comb is great!
Start your W, then your E. - Shortstun+Jump. Use your Q to stun again. Your wave break out and the most enemies are dead , 'cause they thought "Leona mid? WTF , I kill her easily..." - An Ignite is a good finish-move ;)

• Fun :)
• Enemies 'll see you as a "troll" and think "Leona mid? Easy farm!"
• Lot of cc's
• Nice damage ( in combination with Sheen or Lich Bane )
• Great chasing

• High cd's
• Bad escaping
• you 'll be flamed , 'cause others 'll see you as a noob / troll
• Items are EXTREM important in the late game
• If one spell don't hit an enemy, you loose a lot of damage
• Low range
• Bad farming against a range

Leona's power depends on her lane-enemy. She is strong against fast dying champs, bad against tanky. The different is more in the late game than in the early game.

Here some champs which are easy / risky / difficult to kill...

She deals high damage. You have stuns. You have ONLY stuns. But still be careful : One fault of you , and you are dead!

He has one stun - but the most TF are too silly to get this card. Your stuns and your damage crush him fast into the death!

It's Kassadin. Fear him! Stay at tower! He's stronger than you!... and op!:(

He is too tanky for you. Your comb isn't strong enough to kill him, wait for a gank or stun him at your tower.

You can easily jump over her Crystallize. Your comb can "kill" her, but not the egg as well. Let her use her Rebirth. Again your comb and she 's dead! ;)
Tip : don't use Ignite if she didn't used the egg!

Mhm. You can deal him easily damage, but he can do the same to you. If you kill him, his passive ( Death Defied )can kill you easily!

She is strong, but it's not impossible to win against her. Your stuns ( and a bit luck ) 'll give you the chance to defeat her!

Annie is easy to kill ... BUT her stun and Tibbers can make you dead easily!

Akali is a strong opponent, you have to play careful. The main problem is : you have one "easy to fail" - jump, she has three "unfailable"!

Thank you, guys , for reading this guide. I hope i could help you / i could convince you that Leona(Mid/AP) isn't total trash. Please leave a positive or negative critic for me:)
- Any changes to make this guide better? - Just write me. Any mistakes in spelling / grammar / etc. - please tell me ; my english isn't the best :D
Have Fun & Try this build! BYE :)

note :
sorry for using "easy" and "easily" that often :o :D