Evelynn’s early game is very weak and she will be power farming till level 6 so she can become invisible and get her Ultimate R. Try and invade her jungle and steal away her camps to delay her level 6 power spike.
Place Control Wards in the river and go for deeper wards rather than relying on shallow ones. This will help you spot her before she gets the chance to become invisible. Placing wards on her camps are a good way to counter her.
Evelynn wants to assassinate targets that are alone. Group as a team to make it harder for her to execute and kill squishy champions.
Get wards down! Evelynn might be cloaked when walking but not when doing camps. Place vision on her jungle camps rather than inside lane bushes.
Evelynn will look to execute someone before a team fight or an objective spawns. Do not move around the map alone whenever a major objective is about to spawn. Stay as a team if possible.
Keep track of Evelynn’s Ultimate R. When it’s down, she is a lot less mobile and cannot escape skirmishes without using her Flash.
Evelynn gets stronger with kills. Try and reduce her gold income by not overstaying your welcome and getting killed by her. By not dying to her, you will reduce her effectiveness as the game goes on.
Evelynn needs level 6 as quickly as possible so she can unlock her Ultimate R and become invisible. Respect her ganks post level 6 and make sure you track her with good vision throughout her jungle.
If the enemy bot lane goes missing, they might be helping Evelynn take the Drake. She cannot take it alone early, so try to take it away yourself if you’re able to. If not, gank bot lane and take it with them.