Welcome summoners, my name is Hinata Vox and I main support. Leona is my favorite aggressive support and since she has been more popular lately I decided to share my thoughts on her in bottom lane. She is on of very few support who brings a "Go big or Go home" mentality to your lane and I'm going to teach you how to exploit that at low elo.
Pros / Cons
Passive can be proc'd by anyone.
CC with every ability.
Best level 2 engage of any support.
No escape abilities (covered later)
You are HOT ;)
No escape abilities
A good Alistar will always beat you.
For runes I run...
9x Greater Mark of Insight
9x Greater Seal of Resilience
9x Greater Glyph of Warding
3x Greater Quintessence of Avarice
Pretty standard runes for a tank support, with the exception of the Marks of Insight. I run these instead of more armor runes because of Leona's Passive "Sunlight". It helps to increase the burst you can potentially deal in the bottom lane with a good AD that carries abilities with On-hit effects.
For masteries I run 1-8-21 focusing on Health, CDR, and XP. As leona you have the potential to be a roaming support very early and getting a strong gank on mid-lane as soon as you hit 6. More info on this in the Unique Skills Chapter.
For my build follow the items I listed above to an extent up to the finished Shurelias. This is where it becomes decision time...
Is your team starting to teamfight? Focus on finishing Aegis.
Are you losing bottom hard to the AD? Go for finishing Randuins Early.
Is mid getting fed and coming bot? Pickup the Negatron Cloak and consider finishing Banshees.
Is your AD winning the lane almost 1v2? Consider going for a Trinity Force for more damage instead of Randuins and start roaming.
Do you have a stupid amount of kills? Press shift+2 in game.
A lot of people really like to start with q, but I am a firm advocate of starting with your E. This allows you to apply your passive to multiple targets if you can manage to hit both of them at level 1. I wouldn't reccomend a level 1 engage on the enemy unless you can hit this on both your opponents and pulling yourself to the AD carry. Start E, Q, W, W, W, R, this will give you the most AOE damage and tankiness before learning your ultimate. People have a tendancy to underestimate how strong your early game damage is with your W because they think of it mainly as a shield.
Otherwise Max W, then E, then Q, but always R at 6,11,16.
My favorite thing about Leona is that she is an all or nothing support. Unlike other support where you try to poke a little before going in for the kill Leona possesses the strength and durability to go in as early as level 2 and take out 2 opponents from full health to zero if you have a good AD.
Exhaust - Best support ability in the game. 80% auto attack damage reduction can save your carries while slowing the enemy enough to close in for a kills.
Heal - Great for trying to force the enemy into an engage they think they will win. This is Heal-baiting and it's hilarious. Also give you the ability to tower dive at level 5 while your w is active without worrying about being caught underneath.
Flash - I don't like this ability because as Leona there is really no point in trying to escape. You already have a skill that can take you over walls to get a surprise engage but as a pure-tank you should never have to worry about running from a fight; unless you have the worst sense of when to engage. In which case substitute this for Heal.
Leona is absolutely amazing in just about every team comp. The time to pick her is more or less suited on your team's needs as compared to counter-picking since she is so universally good against almost anyone and with any AD. My personal favorite to play her with in bottom lane is either Corki or Ezreal. Any AD with on-hit abilities works really well. If your combo your abilities quickly your passive will apply marks quickly and it's nice to have an AD that can pop them as quickly as you can place them. As compared to someone like Sivir who might not be able to pop your Zenith Blade's Sunlight before you hit them with your Shield of Daybreak.
Your best friend in bottom lane are the bushes along the outer wall. If you can stay in these while they are unwarded your opponents will always be fearful of your interjection to their laning phase and just the thought of a good Leona jumping on them is enough to make them back up.
Don't be afraid to pump fake your opponents aswell. If you want to harrass, hide in the bushes until you feel like you can get a guarunteed hit with Zenith Blade. Pop your W wait 1 second the launch your zenith blade. Try to get a hit with your melee before you activate q because when you hit it the ability resets your autoattack timer giving you a free 2nd hit with bonus damage.
I hope this helps anyone who was interested in trying Leona, she is definitely a top tier support and one that is very pro-active and aggressive instead of passive like the infamous Soraka (I hate her so much). Thankfully if you are good at knowing who to target you can beat any Soraka you come across!
P.S. Once you start targetting someone don't go all out. Wait for Soraka to heal and then switch targets. It's hard to get the hang of but use your zenith blade onto the AD, and when she heals her drop your ult on top of Soraka and get in close. She won't know what hit her and the only ad she can be partnered with that might say something about it is Vayne or Draven.
P.S.S. Don't even try to go after an Alistar with Leona. Alistar is a tank, you never want to target the tank (if possible), but he can also make sure you don't target the AD carry and they will just open a can of whoop@$$ on you first.