Originally Posted by MrFisterRoboto
About her only weakness I can tell so far is that if she gets her blue stolen early game, she can end up behind. However, she's great at pushing lanes, clearing the camps, and making effective ganks.
Her major weakness really, would be that she's vulnerable in the jungle against counter jungling from either multi/short CD gap closing champs (Like Lee) or can achieve near perma-slow status off 20% CDR or less, combined with a gap closer or speed boost Everyone else can be kited for days.. Kayle jungles reasonably well without Blue Buff since her reliance upon it is purely for the sustain, it doesn't help her clearing speed all that much. While losing first blue affects her lvl 4 time decently due to a forced recall, (And really, you shouldn't be losing her first blue to a lvl 1 invade, her lvl 1 team fight presence is insane), it isn't the end of the world for her like it is with Amumu and Fiddles.
Things to note about Jungle Kayle... You got about a thousand viable options for Masteries and Runes, so she really is quite customizable. You can build her for the fastest clear time imaginable with the traditional 21/9/0 Jungle Mastery with the AS/AP/Armor Rune set up, or you can go with a mastery page that skips all the Jungler only masteries and put more into her overall defense or overall DPS, You can even throw your extra 9 points into utility masteries. She is also very open in her options for starts due to the low mana cost on her key jungling skill. Get help on Golems with hard leash on Smiteless Red, and you'll have enough juice to clear wraith, wolf and blue afterwards and be able to gank top or mid. Wolf > Smiteless Blue > Red, or the traditional Wolf > Blue > Wraith > Wolf > Red.... it can be hard for some junglers to counter jungle her in the early game... a Shaco tried to do the cute "Blue > Wait a minute at Enemy Red" start against me... only to find that the red was already cleared and he quickly fell behind due to getting neither a kill or creep steal for the time he invested on my side of the jungle.
As per the items... I don't like building much more than the spirit stone on her as a jungler for the sustain and extra 10% damage on jungle creeps if I fall behind the enemy jungler (And even then, most of the time I don't build the Spirit Stone). The champion damage from Spirit of the Elder Lizard really falls off relative to other items pretty quickly as you build up your A/S in combination with her passive. I like getting Zerker's on her first and following that up with a Zeal to really empower her ganking potential very early on as well as making her very capable at counter jungling. Afterwards, I make a number of case by case decisions. If I'm the only carry capable champ, I'll aim for an IE afterwards while taking significant farm from the lanes should they allow me to and become a full fledged carry in the end game. If I have a carry in the lane, I'll rush a Black Cleaver and Sightstone and make Kayle a moderately tanky DPS and a very strong duelist whose mission in life is to make the enemy jungler absolutely miserable.