Maybe it's just me, but I try to utilize and think with an ADC-like mindset whenever I play him.
Meaning that cautious, calculative plays and good positioning is key. Unlike most assassins, Ekko is fairly immobile champion with a weak early game because his base movement speed is low, his cooldowns are high and he doesn't have quick or reliable evading/escape abilities outside of his ult. Sure, he also has his E - but the dash range on it is pretty damn pathetic. When it comes avoiding the enemies or their abilities, I really only the use the E as an evasive skill whenever I'm in the jungle since it can dash through walls. To take full advantage of Ekko's kit, you have to learn how to effectively time and position your W stun with the rest of his kit. A proper W+R or W+E combo can win team fights and games. I reccommend watching some proplay montages on youtube if you can, so that you can get and idea of what these combos are and how they go.
Or tl;dr - play safe until 6 and learn how to time & utilize your ult and your W stun in teamfights.
Then again, all of this advice for for mid lane Ekko. When it comes to top lane or jungle Ekko then I can't really help you there.