Since comment to vote came off, all I've gotten is downvotes.
It seems to me that around here at MOBA it is a competition for who writes the best guide.
People who are downvoting my guide have either taken a quick glance at the items and masteries, and downvoted, tried the items without reading, and downvoted, or just think my guide is a piece of **** and downvoted it.
Cool. Cool.
I don't think I'll write another guide if people are just going to google "(champ build)" try the highest rated one, and vote depending on how bad they play.
Nothing is more insulting than tl;dr hey look items your guide sucks LOL!, When I've actually wrote in a lot of detail, and it might be worth reading.
I'm tearing the guide down in 2-3 days.
- Oh and by the way, I was the first one here to write a guide that even suggested an Alternative build, with Sheen / Trinity Force, and still the first with Nashors tooth.
GL Moba.
- Afince.

Edit: Fixed masteries on both builds
Edit: Rearranged items in build #2, removing glacial shroud from being build just after Merc Treads.
Edit: Focused HoG start game for build #2.
Edit: Removed Warmogs and replaced with Reverie.
(These items are only suggestions. You must build according to team)
Edit: Added screencaps
Edit: Added build 3
Edit: Fixed mistake in build #2 where there were only 5 items...
Added thornmail + Rearranged build order.
Edit: Changed build #2's runes. Removing Mag.Pen and adding health flats. Noted the idea of selling phil stone/reverie for Warmog's Armor

To anyone who is reading/following!

I am receiving a LOT of positive feedback from you guys! The build is working and its not just me or some fluke!
I've also had a few comments, with mentions of items and things. I do need some items to be tested out. Can anyone help?
Currently mentioned:

Lich Bane. I can see this expanding from Sheen instead of Trinity Force, letting you build Frozen Mallet or any other item.
I need to test it first though. Anyone trying the build may want to take it into consideration!

I can see this shredding up in conjunction with Nashor's Tooth, a great idea mentioned in a comment.

Any and all feedback will be read! I'd love to hear it!
- Afince

Note: Build #3 is something I am testing at the moment. Don't try it if you don't want to, I'm still working around with Guinsoo's Rageblade and trying to find a place for Nashor's Tooth and Lich Bane.
The build is there only to look at, feel free to try it if you want though.

Build #1 is based on 3v3, and build #2 is based on 5v5. DO NOT USE BUILD ONE FOR 5V5.
Leona was introduced only a few days ago, and there was a lot of hype. I was never all that interested.
I tried her just to see what she was like, and I was impressed.
Leona was made to be a tank, but in 3v3, she is a potent gank machine.
She also makes an excellent tank and disable in 5v5, keeping enemies shut down long enough for kills.
Side note: Be prepared to get a lot of assists, or even a few deaths. Most kills will be from your carries. Don't be upset if you don't get the kill, your carries probably need the gold more than you do. If you aren't happy with assists, don't play Leona.

Disclaimer: Please read my guide before jumping in and running the suggested items! Some items work better in different situations! This is the role of a tank!
By the way... this is the first guide I've ever written, especially up for release to the general public. Any feedback is good, and I will respond as quick as I can.
- Afince.

3v3:
Pros
- She can initiate fights
- She has two stuns
- Leona is great for ganking and chasing (Using Zenith Blade + Shield of Daybreak)
- Sunlight allows her teammates to do extra damage

Cons
- Easily harassed early game
- Somewhat slow
- Difficult to farm
- Struggles to counter-harass early game
- If focused can bring down the team

5v5
Pros
- Excellent tank and initiator
- As said before, sunlight helps her teammates rack up damage
- Her ultimate is excellent in a teamfight
- Eclipse allows her to tower dive with minimal damage back on her part
- Lots of CC and excellent disabler/team-mate saver

Cons
- Smart opponents will ignore her in a teamfight
- Her slow speed means she can struggle to save teammates
- Her AP ratio is not excellent on her abilities.

By the way, yes, I suck as Vayne. I got focused like hell. Please ignore that if you can ;__;Another great match I had.
A big thank you to Caladan for testing out my build and giving me some screencaps. :)AP LeonaAP tank3v35v5 build 2 - Tank. If you can't see the scores, Leona got 7/1/17

I've gone with armor pen to fit the suggested items.
Health Quints and Magic Resist Glyphs are fine too.
Movement speed could also be an investment, so could Magic Pen.
Remember, these are only suggestions. Try different combinations!

Exhaust is great. It shuts down any physical damage dealers and lets your teammates catch and chase. The damage reduction is great too. An excellent summoner spell.

Harassing and trying to get away? Getting chased? Need to get that last shot on Xin Zhao?
Flash is for you! This summoner spell is a common favourite for almost any champion.

Alternatives

Teleport is there to compensate for your lack of mobility. A team mate might need a save near a ward, or you might need to push back some minions.
It is always handy.

Definitely a handy skill. It's always great when enemies are trying to push a lane and you smack fortify in their face!

Great for chasing/getting away. Some people prefer ghost over flash, and that is perfectly fine.

Ignite is somewhat 'meh'. Other team mates should carry ignite, not you.

My thoughts on other summoner spells

Heal should only be used if you can't have access to other summoner spells, but really, I do not think it is necessary on a tank. Or at all. Same goes for clarity.

You should not be playing Leona if you need this summoner spell.

No.

Not the best for a tank. If you need it, feel free. It can work, but having it also sacrifices another summoner spell.
Offnote: I have played Sona a bit in ranked, and almost every time, they pressure me into grabbing CV when I desperately need teleport.
However, it is still a great spell, and if you need it slotted on your team and you lack a support, take it.

I will cry if I see Leona jungle.

Can be useful if facing Warwick or Malzahar. Removal of debuffs is great.

Leona is lucky to be blessed with two stuns, one of them also acting as a slow.
Using these skills to their best lets Leona do multiple things.
- She can gank
- She can chase
- She can disable/stun/slow
- She can tower dive effectively

To initiate a team fight or gank:
1) Charge Eclipse. This allows your armor to go up, and allows for the final burst.
2) Hit Q and have Shield of Daybreak ready.
3) Leap in with Zenith Blade.
- Charging Q first allows you to stun almost immediately after you blink.
- Charging Eclipse allows you to have bonus armor in case of:
- Retaliation
- To apply more Sunlight buffs
- To give you extra defense if you decide to tower dive.
4) If they are running away or need another stun, use Solar Flare.
Note: You can initiate with Solar Flare if they are running away.


This is your primary stun. It charges your shield, making your next autoattack deal additional magic damage and also stuns the target.
Note that you can also use this for extra damage on towers.

This is what we will use to chase our opponents.
Zenith Blade is a skillshot, with somewhat short range.
You can use this to gank in the brush, and to chase/initiate.

Your main tanking tool. Your armor and magic resist are increased by a fixed amount for a short period of time, and at the end you burst in AOE magic damage.
Use this while initiating, and also towerdiving.
With a decent amount of CDR, you can keep it up quite often.
Don't bother to use this to farm often. Team mates while just hit the minions you've afflicted with Sunlight, denying you any minion kills.

Solar Flare needs a section on its own.
It is a skillshot, and an AOE.
It can be used for...
- Halting an enemies advance
- Stunning an enemy to catch up while chasing
- Initiating a team-fight or finishing off an opponent.
Remember, you can always use solar flare to save a fleeing teammate!

Sunlight is Leona's passive. Basically, whenever one of Leona's skills is used on a target, they are marked with "sunlight" which when struck is triggered and deals magic damage (depending on Leona's level).
Sunlight is one of the reasons why Leona can gank so effectively with a partner, or due lane with a mage or ranged champion.
She can initiate the gank with her normal skill order.
She will afflict sunlight like so.
- > Hitting with Zenith Blade
- > Hitting with Shield of Daybreak
- > Hitting with Eclipse
- > Hitting with Solar Flare
Considering that Leona's sunlight deals around 200~ damage at level 18 (I cannot remember at this time), means that x4 = 800 magic damage! (If all are triggered)
This makes partners such as Morgana and Cassiopeia excellent.
Their DoT's (Damage over time, for people who don't know) allow each sunlight buff to be triggered!
Miss Fortune is also an excellent partner. Her E skill may lack damage, but if dropped while Leona is attacking, allows all of the sunlight buffs to be triggered.
Factor this in with team-mates and laning partners! Sunlight is a great passive for Leona to have, especially in an aggressive build!
Make use of it!

The idea here is to play tank +/ meat shield. You are also here to save your teammates, and to stun and disable. This is Leona's role.
You will be there for disables with your Shield of Daybreak and Solar Flare, to chase/initiate with your Zenith Blade, and to help tank with your Eclipse.

With items:
You can opt to rush glacial shroud, or nab philosophers stone instead.
Then start building with my suggested items.
Of course, you need to build according to their team! Do not grab Thornmail if you see 4 AP champions and one AD carry. (Of course, unless their Tristana or Vayne is carrying HARD).
Grab force of nature and things with magic resist if they are stacking AP.
Also. Warmog's Armor + Atma's Impaler = NO
You are not here to deal damage. You are the tank and disable.
Also - If you feel the need for extra health, feel free to sell Philosopher's stone or Shurelya's Battlesong and grab Warmog's Armor.

For summoner spells:
I have suggested Fortify and Teleport for two reasons:
1 - Fortify has saved so many games, I don't even need to prove this
2 - Teleport is to make up for lack of speed. Leona is fairly slow.
Other spells can be used if you want. Exhaust helps your team-mates, and clairvoyance is essential, although should be thrown at a Sona or Janna, and not a tank.
Ignite is iffy, you aren't really here to kill. If you want to go kill things, go play Xin Zhao.

For runes:
These are your standard tank runes, and Magic Pen for your sunlight buff.

Masteries:
Common for tank again. Both +1 to Fortify and Teleport, feel free to change these.
Remember, This is only a guide and is not set in stone.

Leona's core will always contain Mercury's treads and some kind of armor (Mostly Randuins due to the gold that is brought from HoG)
Always build around the enemy team or to compensate for your Mordekaiser stacking Thornmail against Malzahar and Sona.

Some would say that it is up to the tank to buy sight wards for the team.
With Leona this is difficult.
Gold is a struggle to get, especially with the fact that she struggles to farm.
Spending 500-1000 gold on wards throughout the game can really put a dent in item purchasing, especially if you need Vision Wards for Evelynn or Twitch.
A few wards is still helpful though, placing them in the brushes along the river to prevent any annoying ganks in start-mid game.

Leona is an excellent champion in 3v3.
ALWAYS TAKE BOTTOM LANE!
Bottom lane for Leona is essential. She is somewhat squishy early game, and she should have a teammate beside her. (Unless you decide to take defensive runes, which is perfectly fine)
Top lane only if you wish to take the risk. If you find that you are opposed with a ranged harasser, take bottom lane.

When going for skills, focus to bring up Shield of Daybreak as much as possible. At level 1 with exhaust and your Q, you should be able to get first blood if your teammates help you.
Zenith Blade you should be focusing next, as it helps you do amazing things.
You know those brushes above the red buff? If top calls for a gank when they are hiding in the brush, you can jump in from the lizard and take them down.
Eclipse should be focused last, but you should aim to get one point into it before level 4.

Abuse her sunlight buff as much as possible! You can pop 2-4 buffs while killing an enemy depending on your teammates and your skill usage.
You should focus to attack in this order: Charge W + Q - > Leap in with E - > Exhaust+/2xAutoattack -> R
If you have a teammate like Morgana ganking with you, she should be aiming to pop all of the sunlight buffs while dealing damage.
Leona cannot do 100% damage on her own, but with a teammate she can crush an opponent if an ally is there to support her and pop the buff.

Items:
Rush philosophers stone start game if you can. The extra gold should help to try and compensate for Leona's difficulty to farm.
Her core consists of only Philosopher's Stone and Frozen Mallet.
Most of the other items I have been testing out at the moment. If you feel the need to play tanky, feel free to drop Nashor's Tooth + Gunblade for Randuin's Omen or Frozen Heart.
Philo can be upgraded to Shurelya's Battlesong for that speed boost, or you can go ahead and sell it for an alternate item like Force of Nature or Thornmail.
Do not forget that my items are only suggestions. Always build according to the enemy team!

Please note that offensive items like Sheen and Berserker's Greaves are only advised for 3v3.

(For 5v5, do not go for items Sheen Nashor's Tooth and Trinity Force, DPS Leona will not work 5v5, especially in a teamfight where she can be better placed as a tank. Philosopher's stone still works early game, but I recommend Mercury's Treads and armor/tank items like Warmog's Armor and Thornmail.)
Start game:
Philosopher's Stone
It is essential to grab philosophers stone as soon as possible.
Why? Leona has difficulty farming, and spamming your skills only lets your teammates take your minion kills via Sunlight. The gold and regens are essential early game.
Late game, you can build this either into Shurelya's Battlesong, or Eleisa's Miracle
Note: If you opt for Eleisa's Mircale, do not get Mercury's Treads. Tenacity does not stack, unfortunately.

For boots, I suggest Berserker's Greaves. Mercury's Treads are fine also.
Mid:

Sheen is essential. It enables you to do massive damage when bursting via Zenith Blade -> Shield of Daybreak. Your shield is your hard hitter here, and Sheen makes it that much stronger.

Nashor's Tooth provides you with the attack speed you need for effective farming. The CDR allows you to burst more often, and the ability power is always nice.

Standard for DPS'ers. Phage gives the nice slow, Zeal lets you move faster, and you get a bigger boost from Sheen.

Optional items

Tank

These are your standard tanking items. Xin Zhao driving you insane? Grab Thornmail and Randuin's Omen.
LeBlanc needing to be shut down? Force of Nature is perfect for you!

Utility

Since you will begin with Philosopher's stone, Reverie and Miracle are great utility items. Eleisa's Miracle gives you Tenacity, enabling you to run Berserker's Greaves, while still getting the tenacity boost.
Feeling slow? Shurelya's Battlesong can help! The speed boost can help you and your teammates chase or run away, and coupled with Randuin's Omen, lets you have your enemies on their toes. The bonus health and regen is great, too.
Frozen Mallet lets you chase your enemies, giving you a nice slow and a lot of bulk.
Note: I do not advise building Trinity Force and Frozen Mallet on the same build.
Run Frozen Mallet for tank, and Trinity Force for DPS/Tank

Other items that need mentioning

: Everyone loves a spell shield. Catalyst the Protector helps you stay in lane. The health and mana bonuses are nice too.
: An excellent support item. The aura assists your teammates and is great if you feel the need for it.
: Want to play meat shield? Sunfire is great for a full tank set, allowing you to rack up some extra damage while getting a nice boost in armor and health.
Giant's Belt I've always found to be annoyingly expensive though, just a thought.
: If you want to play tanky without getting Frozen Mallet, get this. Works well with Sunfire Aegis.

Always, and I mean, ALWAYS, build according to the enemy team!

See 2-3 squishies?
Build tanky dps, or build for ganking. Either is fine.
Seeing Mordekaiser Cho'Gath Alistar Blitzcrank Amumu?
Counter-tank. Build tanky items and support your DPS'ers in taking them down.
Make sure you check to see what the opponent is building!
The sole role of a tank is to stay alive and take damage.
If you are facing AP-oriented teams, consider these items...
Banshee's Veil Eleisa's Miracle Force of Nature
If you are facing an AD-oriented team, try these...
Thornmail Warmog's Armor Sunfire Aegis Frozen Mallet Frozen Heart Randuin's Omen
Keeping these ideas in mind, you should be fine to either tank or to gank.

A quick note on Guardian Angel:
I recently tested it out. I do not recommend it that much. If you find yourself dying a lot, go ahead and use it, but if not, any alternative is better.

Leona is quite a fun champion to play. She can be build so diversely. However, my 3v3 build is far different to my 5v5 build.
Stay tuned for my 5v5 and complete guide!
- Afince