Primarily due to the +20AD from runes, on her AA reset.
Run Klepto or Dark Harvest With Domination or Inspiration secondaries. Magical Footwear+Futures Market. Or, Relentless Hunter+Whatever you want.
Build order is 
From here the matchup and the pace of the game is going to determine what you build/complete next.
But a full build is going to be
(Cinderhulk)
or 
(Situational) you could build other things, if this doesn't really make sense for the match.
MorgManBasher11 votesWhy on earth would you ever run klepto on a jungler Is this mobafire
GelsominoKiller5 votesYou clicked on a jungle Leona post, what did you expect, rocket science?
Illabethe7 votes20 AD? What? The variable runes only give .6 AD per point of Adaptive stat.... so it's giving you 12. Ofc..... isn't Leona's base default stat AP?
P.S. AP Leona clears jungle and ganks stronger than AD, because it's accompanied by both CDR and Move speed.
Warlord Rhinark1 votes20 AD? What? The variable runes only give .6 AD per point of Adaptive stat.... so it's giving you 12. Ofc..... isn't Leona's base default stat AP?
P.S. AP Leona clears jungle and ganks stronger than AD, because it's accompanied by both CDR and Move speed.
The new rune shards give 10 Adaptive Force.
Pick two of them and it should give you 20 AD.
Illabethe4 votes[{quoted}](name=Warlord Rhinark,realm=EUW,application-id=3ErqAdtq,discussion-id=8PiLIxzJ,comment-id=00010000,timestamp=2018-11-23T07:52:45.739+0000)
The new rune shards give 10 Adaptive Force.
Pick two of them and it should give you 20 AD.
Hover over the damn word "Adaptive Force" It'll give you a tool tip.
Warlord Rhinark1 votesHover over the damn word "Adaptive Force" It'll give you a tool tip.
I wish pressing the "show extended descriptions" button at the bottom of the Rune Page gave the tool tip by default.
FCJAAAAGOOOO1 votesWell, that's one thing I'm okay with this season I guess.
CLG Factor1 votesokay so I tried this, and what am I supposed to do when the enemy steals ur camp over the wall at lvl 1, cuz leona cant clear worth shit
PhearBunny1 votesYou can actually run Aftershock as well if youd like, since the adaptive force isn't limited to a Domination tree. And she doesn't have an issue clearing by any means. Time your AA reset correctly, and her clear time isn't bad by any means. Is it bad compared to Shyvana? sure. Is it bad compared to Nocturne, Xin, Lee? No. AA>Q>AA> repeat. Skip raptors and golems on your first clear since her initial clear is weak on multitarget camps, once you upgrade your machete she clears anything quickly. Her biggest flaw on clearspeed is a lack of mobility, which is primarily why I was priotizing a Kletpo or Domination build, to compensate for her lack of speed. Magical footwear = speed. Futures Market= Earlier Mobis. Relentless Hunter = speed. Approach Velocity = speed. Klepto = faster Mobis(Her Q synergizes well with it, and there are matchups where itd be ideal) Just like there are matches where DH would be ideal, or where aftershock would be ideal.