here is my personal list of what i think are the best junglers.
-S tier (reserved for champions i believe are effective and very easy) :
able to engage and disengage , just needs black cleaver and has superb damage throughout the game
olaf is early game and some of the highest level 1 dps thanks to his q cd reset he is able to turn into a lategame monster as he cant be kited as easy in this map.
#3 Jarvan iv Jarvan is known to be a very good 3v3 champion, he actually one of the very few champions to be nerfed exclusively for this map along with wukong, his combo is does good damage even if he builds tanky, his utility is also too good too pass up, with team attack speed steroid and massive aoe potential especially after the R buff.
not much to say here, this guy can jump from the comfort of his jungle all the way to the lane leading to some easy gangs and counter gangs, he pretty much forces everyone to play passive but he falls off lategame if they are not many glass cannons in the enemy team
This champion is major cheese, playing it in 3v3 feels like cheating, thing is riot doesnt really care about balancing champs for 3v3 much, poppy can just come to your lane close her eyes and land all of her combo and her E stun thanks to the very narrow spaces found in this map, not only riot doesn't adjust this but they actually going to buff her W movement speed and E stun duration to 2 seconds at all ranks just because she is weak in rift right now.
-A:
extremely good 3v3 champ but imo he is better off laning
good early game but if you dont capitalize on that , you fall off super hard against the usual bruiser 3v3 comps
His early clear is insane, he can pretty much clear jungle faster than most champs and at full health, he can then invade enemy junglers monsters and make his life hell. he is still kinda squishy though and he falls off hard against strong front lines and cc tank.
He is super easy to play, clear jungle like its no thing and can destroy almost every champ in 1v1, his ult can be a nice addition to a hard engage team but, zhin cant afford to fall behind and he is not the best champion against hard cc tanky teams.
Although a lategame champion, this guy can clear the jungle so fast and gain so much gold that he turns to mid to lategame unkillable menace in no time, he W and pillar also bring alot of utility to the team, pillar can even block out most entrances in this map effectively shifting the map landscape as he wishes.
-B:
any sr jungler can work, even the lategame strong ones like amumu and master yi, tt jungle is actually very rich and if you clear it fast you can be bigger than the laners, making it perfect place for scaling junglers.
-C: Duo lanes with smite, duo lanes with adc-support are very common in higher elos, adc usually take smite and farms jungle or does counter jungling all that while they bully a 2v1 lane,
be a man and do that pussyass shit.