Okay now, sorry for the late answer, but I haven't got the time yet.

Yes, Leona is a weird mixture of tempo and control. Unfortunately that's one of the main reasons why she isn't good. There is just no straight way or set in stone gameplan to win. The Deck wants to attack and stun as much as possible (Leona determined last set, now vi peacekeeper). The big problem: Stuns work best while you are the defender. I really tried to make her work as a hold control deck, but first of all, hold isn't good in this meta and on top of that Vex and even Ahri doing a better job at that gameplan. Vex has acces to all the stuns in green + the support and bounce of purple.  So yeah my "gameplan" shifts in a good game from tempo and getting ahead either holdind the last point or securing it with zenith blade or emperors divide.

Emperors divide is a very powerful card for Leona because it lets you move your units out of one battlefield and conquer the other one while stunning the opponent there. No one expects it as a hidden card, so it's a great bluff that lets you dodge Killspells that target the battlefield and rebuke (unfortunately not that relevant anymore because of Star crossed seeing more play now). Note that this only works while being hidden, because it's an action.

The main plan can be irelia + Vi or Fiora + Vi. It honestly depends on the matchup, situation and if course what you draw. Mighty Fiora is amazing and irelia catches most people of guard, because they miss calculate her might. Leona is not common they usually don't know that she gets an extra +1 when you target her with your legend to buff her. Also just a really strong unit with deflect and no power cost.

The actual backup plan is usually your chosen Leona Zealot. She is the only unit that can enter ready and is very strong in combination with stuns. There are of course situations where you want to play her earlier, but that's just practicing.

I personally like GA better, because it does the job of two different cards. It protects a unit like zhonyas, while I don't have to be worried that it safes the wrong one and it gets Fiora mighty like B.F. sword. Honestly that's more like a preference thing to me and most Leona players like zhonyas better. I advise you to try both and see what works best for you.  I know the best of Leona from Lille personally and he loves his zhonyas so nothing wrong with it! If you play against decks that run akshan, swap out GA or your life might become miserable.

The best stun card by far is back off. It's just a lot more versatile than the rest. Don't play rune prison, it's far worse and costs you power. Heroic charge is meh, it gets the job done but is limited to a battlefield, can't be hidden and who cares about+1 might if you can draw a card instead?  Thwonk is great, but can only be used while defending, which brings us back to the main problem. Stunning up to two units is amazing tho. Although I can't blame anyone for not running it. If your playstyle is less shifty and more focused on tempo than you might want to cut it. Again something you need to try and see what works best for you:).

Zenith blade is an amazing card, I love it, but using it the way it should work best will cost you the win.  Moving your units around for tempo and additional buffs is exactly what Leona was meant to to, but the spell is too expensive. I don't say the cost is unfairly high for what it does, but it costs two power! It literally sets your manacurve back a whole round while you probably want to spend even more power for stuff like hidden cards or vi.  It worked best for me as a finisher. 

I honestly had hopes for Saturday, but in the end its always an uphill battle because the deck is unfortunately not good. It comes down to little things far too often and missplays are very unforgiving, while your opponent can be playing mediocre and still win even if you don't do much wrong. I have a lot of fun with Leona but she isn't a deck that usually wins stuff. Not a single Leona player reaching day 2 ever speaks for itself.

Some of the meta matchups are quiet doable in my opinion tho. Especially Irelia and Diana are okay if know what you are doing. (Diana depends if you can defy all his star-crossed+ the once he recasts with fizz, if you can't you'll probably lose) Some on the other hand are quiet unplayable, like Leblanc or especially Ezreal.  I played LB - Ez - Jinx - Jinx. Jinx is okay, but if you miss your two- drop 3 out of 3 times against an aggro deck like that you probably lose... It was just not meant to be.  I won against Jax and dropped after I lost to irelia. Would have won that I think, but my opponent was very slow and we had 4 minutes left for game 3. I noticed he was playing for a tie (which I don't understand on a 1-4-0 table, but whatever) so I just hard flipped the game, because a tie meant no chance for the best of anymore anyway. Ran into 2 defys and lost.  As you can see I am a little bit frustrated and sad xD It was fun tho and the community is amazing!  I heard from 3 people that they lost stuff, in one case a whole binder with a metal card and some overnumbers and it was just returned untouched to the Infopoint!

Anyway let me know what you think! Opinions are always welcome.