Who is Ekko- Ekko is a mobile diver mage/assassin with huge outplay potential. In the hands of the right player Ekko can carry any games
When to pick Ekko- Ekko works well when your team is comprised of all AD, or have divers/assassins that can go in with Ekko.

Synergy-As a relatively squishy diver, Ekko works best when paired with other dive champs or supports that can heal, revive, or peel heavily for you. I’ll break this section down into each lane
Top- Ekko works well with disruption tanks like Maokai, Galio, or Shen. The last two especially can follow up on your dive and peel for you while you deal damage. If you have a champion like this it is probably better to go full AP. Pseudo tanks like jax or yasuo who are generally slippery and hard to kill can dive in with you, but you might be better off going tank.

Mid-Ekko once again works well with divers/assassins, or people with good CC that you can follow up on. If your team has divers/assassins like Zed, Yasuo, Akali, or Talon you should go in before them and try to land a W, and if you dont, use stopwatch/zhonyas. As the enemies are waiting for you your midlaner can dive them as well, and if they start focusing your teamate it is very easy to land a good Chronobreak that can change the course of a fight.
With AP threats like Vladimir, Veigar, or Cassio that are pretty much always threats to the enemy squishies, it might be better to go tank and get Abyssal Mask in order to amplify your midlaner’s damage

Support- Ekko works well with supports that peel for him well or can get him out of slippery situations. Supports like Karma, Nami, and Janna that shield or heal Ekko as he goes in, and speeds him up, are good if you have a harder time getting onto the enemy without using Flash. Supports like Nautilus, Alistar, Thresh that can CC the opponent so that Ekko can land his W are also good, and can provide some peel in case things go wrong. Zilean also works very well with Ekko, because he can put his time bombs on Ekko and speed him up as he dives. Ekko can go in without having to back out of the fight with R. After disrupting the enemy, if Ekko is focused down Zilean R provides Ekko with his cooldowns again, and if the enemy team is stupid enough to stand on you Ekko can get a huge ult.

Q-Ekko’s main damaging ability. Early game Ekko’s clears are very weak, so you should try and kite camps by using your abilities, then just walking away for a few seconds until your Q gets back off cooldown and you can throw it out again. You can cancel the Q animation by casting Q while in mid dash from his E

W-Ekko’s only hard CC. Ekko casts a circle around a target area, and a few seconds later if Ekko is standing inside the circle he gains a shield that scales off AP and stuns any enemies inside the shield. This is the ability, along with his ult, that makes Ekko so tanky-even if he goes full AP late game his shield basically gives him another health bar. When fighting make sure to cast W either before you go in or to a spot you think the enemy will run to, for example in behind the enemy if he is running away and behind you if you are getting chased. Always start this ability when going JG.

E- Most of Ekko’s mobility. Ekko performs a short dash that can go through walls, and for a few seconds he gains increased attack range, his next AA dealing increased damage and blinking to the target. Has great synergy with sheen items. Also is an AA reset. Use this ability to dodge cc or get on top of your targets

R- Probably Ekko’s most well known ability. After hitting 6, Ekko gains a “shadow” of him 4 seconds into the past. Using R teleports Ekko to his shadow and deals massive damage to all enemies around him, and heals for a large portion of all damage dealt to him in the last few seconds. Extremely potent for diving or escaping. Use this after using W and/or stopwatch/Zhonyas for huge outplay potential. Another cool trick for Ekko jungle is that you can stand in a jungle camp, back, quickly buy items, and R back into your jungle, using it as a pseudo teleport. Don’t be afraid to do this early/mid game because Ekko’s ultimate has a pretty short CD

Early Game-
99 percent of games Ekko will start bot side, simply because Ekko has a garbage early clear. Ask for your bot to give a hard leash, and for top to ward your other buff, because any decent jungler will invade you. After taking your buff take the multi-camp next to it, for example take raptors after red and wolves after blue. After your first two camps, if you see the enemy jungle on the opposite side of the map go and take his other buff, then go grab scuttle and look for a gank. Most games Ekko will just clear until his first back because he doesn’t do that much early game.

Ganking-pretty much NEVER gank before level 3, unless your laner is being hard pushed in and has good, easily landable CC like Jax, Riven, or an engage/hook support like Blitz, Thresh, Leona. Ekko always goes W-Q, and cant do enough damage to secure a kill without his E unless you can follow up CC with your W. After 3 Ekko can gank pretty well. What most ekkos do wrong in the jungle is that they place their W too far forward, on top of the enemy laner. Obviously once he sees you the enemy is going to run away, and your W is wasted unless your laner can provide good engage CC. Place W behind the enemy laner so that when they are running away, they will be forced to walk around the W and end up taking much longer to get back under turret. Often times this wasted time will result in as much time gained as if you landed your W. Engage with E-Q, blinking to your opponent and canceling your Q animation with the E blink, then follow up with an auto to proc passive and run down your opponent. Against most targets Ekko and his laner will have the damage to kill all but the most slippery of opponents. After hitting 6 diving becomes very easy with Ekko, just run down your opponent and R away from the turret, healing most of the damage done.

Ekko is pretty bad at dueling early game- if you get ambushed/caught out against most junglers it probably means at least a flash blown. However Ekko is pretty good if you can suprise the enemy. If you’re hiding in a bush and the enemy jungler is walking towards you, you can W in the bush, and when he gets closer use auto-Q-auto, proc passive. After this you can either run away, having chunked out the enemy jungler, or keep fighting and use e if he tries to escape. Be careful of the enemy laners collapsing on you though, early game after Ekko’s cooldowns are blown he doesn’t do that much for a few seconds.

Objective control- Ekko probably is one of the best junglers at stealing objectives. When the objective reaches low health(obviously different based on when in the game it is), W on your opponents, wait a second or two, E in and blink onto the objective, hopefully proccing your W and proceeding to get a free smite, say sayonara to your opponents and blink out with R. Make sure to time your W so that the stun goes off like a few hundred health away from smite range.

Mid-Late game As the jungler, your goal isnt to output as much damage as possible, but to create as much disruption as possible. Go straight for the backline once a fight breaks out, and try to proc W. DO NOT hold on to your R until the last possible second, it is always better to R if you feel you are in danger of losing the fight/dying. Ekko’s ult is on very short cooldown and you will be able to engage again. Many ekkos suffer from overconfidence, constantly throwing themselves into the enemy team. If you are the strongest member of your team, make sure not to give up your bounty as this will put the enemy back into the game. Instead constantly probe the enemy with E, and if you can get onto a squishy target try and burst them down fast, and then immediately escape with R unless your team is in position to follow up. As ekko you can force the enemy to back alot by diving in, dealing some damage, and ulting out, forcing your opponents to go back home and heal up while you stay full health. Use this number advantage to push turrets or threaten an objective, instead of going for kills every time.