This is just a copy and paste of the guide i left on gd a while ago. Figure i oughta put it up here as well
Leona really *is* a viable jungler. But many are skeptical still. So i'm gonna outline quick how to go about it (or at least the way i go about it).
Before i get started, i just wanna point out that, by doing it this way, I've been able to achieve a 3:57 lvl 4 time with no help (about on par with Nautilus, iirc) and maintaining reasonable health throughout (about 400 at lowest, and that's right before hitting 4). Naturally, with assistance to start this improves by quite a fair margin and may not even require the use of all your health pots by the first recall. In practice, I've typically been able to keep up with (and occasionally outlevel, with good ganks) the opposing 'typical' junglers.
*i have been able to get this time lower, down to about 3:50, with going to double golems (rather than backtracking to do wolves before red), but it also resulted in having about 200 less health, which is too low for me to consider 'safe'. It's possible, but not safe. In practice neither route matters much anyway; i don't jungle til i'm 4, i usually gank after hitting 3.
Anyway, onto the guide.
-masteries: I go 21/9/0. Most of the points are in typical physical damage masteries... AD, armor pen, and %damage amps. And of course the extra damage to minions/monsters. The exception is i take cdr rather than AS (the AS isn't noticeable, the cdr can be), but it's not necessary to do so. Also i've got a point in summoner wrath, because i run ghost on most melees, but that can be thrown in destruction or wherever if you don't want that. The defensive masteries are pretty typical too... hp, hp/level, reduced minion damage/reflection, and summoner's resolve.
-runes: I've got flat AD reds and quints, armor yellows, and flat cdr blues... the flat cdr blues aren't necessary, i just prefer them, again. But the rest is pretty much needed.
The reason for all the offense is... well, Leona doesn't innately have much damage. She needs those early game bonuses to get started with a decent time. The reason for the AD runes? Well, i'll explain more in a bit, but for now i'll just say it's better than AS.
-starting item: obvious choice, machete and 5 pots. Machete is a big part of the reason this is viable... the lack of machete in S2 is (among other factors) what held jungle Leona back. It was do-able, but much slower... cloth armors didn't exactly go very far in boosting your damage.
-skill order: Q at level 1. W at 2. E at 3. After that, max W (and R, of course). The second max is up to you. By the time you get that far, it won't matter in the jungle, and there's perks to leveling each. But i prefer E.
And now I figure most are wondering why they should start Q, rather than W, which is an AoE nuke with a defensive steroid. Well, a couple reasons... the main reason is because Leona's Q actually has two auto-attack resets, one upon activating the ability, and another immediately following the enhanced attack (you have to issue another attack order in order to get the second reset, if you don't give an attack order she'll just take her sweet ol' time attacking with normal timing), allowing her to pull of a quick 3-hit combo in about one second, which far exceeds the (single-target) damage dealt by W. Furthermore, you stun the pack leader with it, and you stun at a very opportune time by opening up with this combo... the stun lands just before the leader is about to strike you, and when the stun wears off the leaders gotta wind up the whole attack again, wasting a bunch of his time, and preventing him from hitting you. That stun duration, combined with the more rapid damage, allows you to kill him more quickly while losing less health than if you start W.
This is also the reason for AD runes... this combo doesn't get as much returns from AS as it does AD... it partially ignores AS due to the resets (but of course fully uses AD on each hit). And it will be the bulk of your damage on the pack leaders (especially the small camps). You won't need to use very many regularly timed auto-attacks beyond this combo and your W, so AS just is slightly slower for the initial clear.
You max W first for pretty obvious reasons... its your defense steroid, its damage goes up by the most per level, its AoE, and its cost is static. A point in E is third for ganking, naturally.
As for the run itself, typically you'd want to do:
wolves>blue>wraiths>wolves>red(>wraiths again for level 4, if you want) for the safer route, and since your smite will come off cd as you get to red.
But this takes a bit of time in getting to red, which means it could be stolen or you could be ganked there. Instead, I typically prefer to just get a smiteless leash on blue, and either immediately go to red or do wraiths then red. Either way, after red you should hit 3, which means you've got all you need to gank, and you should be healthy enough to do so.
For the most part, you want to stick with using W and Q in the jungle. E is AoE and can help, but it's not much damage early and you don't wanna waste the mana unless you've got blue. If you've got blue, go for it.
Your first item should be spirit stone (and ideally you should buy boots at the same time... it's not tough to stay out long enough to get the 850 gold required for both, but if you soak up some damage in ganking or whatever and have to recall before getting that much, get the spirit stone first). Once you've got spirit stone, you're pretty much alright for sustain. Between your own regens and the heals from small camps, you should be able to sustain mana and health reasonably well. The buff camps will still hurt a bit, but not too much, just make sure you've got smite up for them and you'll be fine. You may or may not want to take the second blue... it's kinda up to you. You're not fully dependent on it once you've got spirit stone, but you will have to manage your mana a bit more (no E'ing in the jungle) and you will slowly use mana a bit faster than it regens even so. Not a big deal either way, though
*since people have brought up doing alright with madred's/wriggle's, i'll add that spirit stone isn't really necessary, but it's my preference... it's cheaper than wriggle's, builds into more impactful items and offers mana sustain that wriggle's does not, while still having a comparable clearing ability (due to the 20% amp on monsters and 10 true damage on hit)
After that, just build whatever you want, honestly. Spirit stone (or wriggle's) really is pretty much all she needs to jungle. And with jungle farm (instead of support farm combined with support expenses) you can actually build influential items. So just build whatever you/your team wants/needs.
And don't forget to gank... I'm not gonna bother guiding you through that, but it's not tough. A landed E can often be enough to force a flash. And her ult is ridiculously evil with its range and followup. But just one tip on the ganking front: don't expect to kill the target by yourself. As Leona, you really *need* your ally there to deal damage, even if it's just auto-attacks from a mage (ignite is a little more ideal to proc your passive, but it's not always an option). Your passive hides a lot of damage that you can't access alone, so don't expect to be able to walk up to a lane and kill an opponent 1v1, even if they're weakened (seriously, i tried to take on a jax who had no mana that just took out my top... i had full health, he had about 300 left after my burst and i still couldn't take him out alone)... it takes some getting used to to realize how much (or little) you're capable of alone with her
And that's pretty much it. Go ahead and try it, you just might like it (and see how viable it really is). You can thank me later ;-)
Feel free to ask any questions, too
(and if you feel like seeing my history with it, it's on my summoner named 'shppy'... i'm intending on doing nothing but jungle Leona for a while, so there'll pretty much always be 10 games to look through)
So i've done a bit more playing around with runes, and put some more thought into using AD vs. AS runes. In testing, AS runes were slower for my initial run. On a level 4 clear, with AS reds and quints, i got a 4:00 level 4, while ADs got me a 3:57 level 4, both leaving me with the same amount of health (plus or minus a wolf crit). So on the surface, AD made more sense to me at the time, since the starting run was what i was more concerned with.
But now that I've put it into practice many times, i doubt it's much of an impactful choice in an actual game where leashes are involved and ganking before doing a full clear is more likely... the strength of my leash and gank openings are far more likely to modify my time by larger values than the difference between AD and AS makes.
So i'm gonna point out here that both are perfectly viable, tried and tested, and really it's just a matter of personal preference. Technically speaking AS is more beneficial late game (Leona gains 2.9% of her starting AS per level, vs gaining 5.17% of her starting AD per level, or 6.32% with the AD/level mastery included, so the extra AS will provide more of a dps amp to her natural stats late game than the AD, while providing just slightly less early game). However, that assumes the ability to attack using your full attack speed (not having to move much or at all between attacks) which is fairly unlikely even against slowed targets. Still, AS benefits some potential effects more (wriggle's, wit's end)
Now that the jungle's been slightly reworked again (small camp leaders got more hp while the little guys lost some), I figured I'd update with a re-evaluation of sorts. I ran some quick tests with the current jungle for her initial clear time, and there's been some minor changes. For starters, for a level 4 clear, avoiding double golems, I wound up with about 100 less hp than before, whether I used AS or AD runes. The time for AD runes remained roughly the same, 3:57. However, AS runes saw some improvement, now allowing me to clear with about a 3:57 time as well (actually about half a second ahead of AD).
The reason for this is mostly because, prior to the changes, many of the smaller monsters in the jungle died to 1 or 2 autos with AD runes, but took 2 or 3 (respectively) with AS runes. 1 or 2 normal speed attacks still takes less time than 2 or 3 boosted speed attacks, so AD runes cut a few seconds off. Now, with the readjustments, there are fewer cases like that (there's still a few, but not as many) so many of those little guys take the same number of hits whether you've got AS or AD runes (in which case AS kills them faster). So a few seconds were shaved off the AS time, to the point where it appears to be slightly faster.
Anyway, the point is it's now pretty much even, between the two, for solo clear speeds. And in theory taking AS runes scales better for jungling beyond the initial clear (and is technically better for auto-attacking dps as you level up), so it may well now be your runepage of choice, especially if you go the wriggle's route.
Personally, after playing a few games with it, I still prefer AD, myself... AS doesn't help ganks much, if at all (while AD does, with the auto resets on Q), and AS, while 'technically' better for dps as you level, is only better if you can continually attack at max speed... that often is not the case outside the jungle. AS is rarely the limiting factor in the frequency of Leona's auto-attacks (at least for my style), more often you're limited by the time required to get back into melee range to attack again (as opponents you should be trying to fight/cling to are likely going to try to get away)
Aside from the initial clear and the AS vs AD issue, the changes had some other (kinda nice) effects. For starters, there's more gold. Always a plus. The extra life of the pack leaders means you do take more damage (since they're alive for longer), which hurts a bit on the initial run, but doesn't feel like much of an issue once machete's upgraded. Also, the diminished hp on the small guys actually is pretty cool for Leona. Prior to this patch, her AoE wasn't quite enough on its own to take out the small monsters quickly (at least not without sunfire or lizard spirit), so she had to spend time auto'ing them early/mid game. Now though, that isn't necessarily the case... W and E combined can deal enough damage to pretty easily kill the small guys (at least with the %amp from spirit stone), so her continued jungling feels a bit faster (it didn't need it, but it helps)