ABILITIES AND WHY THE ORDER LEVELED MATTERS

There's really no reason other than cdr to Max "E" (Zenith Blade)
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Maxing "W" (Eclipse) is what gives Leona her main source of defense. It not only gives her armor and magic resist but is her 2nd most damaging spell and is AoE. It's great for tower diving, providing extra damage to all those hit with her passive and tanking the main sources of damage. When the spell is activated it lasts 3 seconds and if she hits an enemy the resistance stats last an extra 3 seconds.So 6 seconds in total you're a walking wall.
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Leona's Q (Shield of Daybreak) is what really gives Leona her lock down power and peel expectations. Maxing it second is vital because without enough cdr you won't be able to be the stun bot everyone on the team loves. You'll become a really tanky 40 damage auto attack minion pretty much.

Try to leave a dent

Leona is a very tanky support who excels in roaming and soaking damage.
0/21/9 is what I'd take on her because her play style of diving and sitting on champions either peeling or locking down helps her survive until backup arrives to help against her opponent or the player she's peeling for kill who she's peeling or escapes safely. W also scales 20% bonus armor and magic resist. She doesn't need offensive stats at all to become a major threat. The 9 points in utility mainly compose of Surviving lane phase and mobility. Having cool downs on on summoner spells is rather important because with exhaust. In a fight Leona can lock someone down, exhaust, and then lock someone down again. Pretty much immobilizing their fighting chance.

This is a really basic version of what your runes should look like as Leona. Some people may run 2 hp quints and 1 magic resist or 2 hp quints and 1 armor. I choose seals of hp over armor because of last seasons rune change. Marks are usually meant for damage but in this case we're gonna roll with armor. It's not to much a difference of seals and makes the option of hp seals worth. Magic resist will always be glyphs or cdr. Depends on your play style.

LANE PHASE MATTERS

If you're going against a strong counter of Leona. I recommend skipping the ward and just buying all hp pots with relic shield. I know, not buying a ward? That's a mistake... But you should both have warding trinkets anyways. Use them correctly and lane phase should be a breeze avoiding ganks. It's mainly helpful against supports whose poke cost a high amount of mana because early game they're bound to run out eventually.

Difficult Really

Really you want your Targons pretty early for the amount upgrading goes it's actually quite good for its price. Also You don't have to instantly buy sight stone. Just start out with a health crystal and boots. But don't not upgrade to sight stone. Vision is probably the most vital part of league of legends game play.

Situations

A lot of the pro guides always recommend Mobility boots because it's cheap and effective. And if that's your way to roll just buy that instead of merc treads. But Merc treads Provide the tenacity and magic resist stats that you can use. When given the alacrity bonus you can have 5 more speed than swiftness boots. Sightstone is what you'll upgrade your Health Crystal into. Helps provide vision of objectives like dragon and enemy invasions in the jungle. Kindle gem is one of your next go to items because as a support like Leona. Health and Cdr are her best friend. It also goes into targons bracelet to become face of the mountain.

Kindle Gem

If you're against a heavy ap team I'd recommend leaving targons off to the side and using it as a source of income and hp. Getting iron solari is more beneficial anyways since it provides global stats and gives everyone in the radius a shield to help fights. Plus the Extra 400 hp and cdr to go along with Leona's best attributes.

Items such as negatron cloak, Chain vest, Giants belt are all situational as to what you'll need to stay alive and will be explained in the next chapter.

Leona needs at least one of these
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CHAIN VEST INTO RANDUINS
Randuins is a very nice item for peeling. Again health and armor are pretty important on leona and the extra AoE slow active it gives you can either be the deciding factor if you and your adc or just you or just your adc escape to a safe distance.
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CHAIN VEST INTO FH

It's important to be tanky and still have stats that can help your adc.
The armor and cooldown reduction + attack speed reduction on nearby enemies really deprives most adc killers like Tryndamere. The cdr gives you more stuns. The armor makes you a lot tankier and you also gain an extra 400 mana so you don't ever really need to worry about running out on leona.
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CHAIN VEST INTO SUNFIRE

This build path is mainly for tanking damage and trying to provide damage on who you're focusing. I'd say build this mainly if your front line needs help more than your back line.
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NEGATRON CLOAK INTO BANSHEES
Please take this path if you're having trouble with poke. Health, magic resist and hp regen for survival. It's not the best thing to build really but if like some cases. Their team is very strong with poke like velkoz or nidalee or lux. Any long range caster that is hard to avoid. Buy this item, nothing wrong with its stats and its passive saves you from damage occasionally.
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They should really explain them selves
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End Game Build #1 is for team survival and peeling while giving decent stats to Leona.
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End Game Build #2 is more for self protection against ap teams.
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End Game Build #3 is all about Leona going balls deep front line status doing her hokage stuff and wrecking the enemy carries.
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End Game Build #4 is nice when peeling heavy ad champions like tryndamere and taking no damage from the enemy adc.
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