my personal core build is [runic echoes, sorcerer's shoes, hextech gunblade, lich bane]. when completed I can obliterate any squishy in a split second and impose fear in the enemy team. the other two items are situational. if you're behind you can change gunblade for protobelt. it's cheaper and is extremely good for surprise ganks, giving the enemy virtually no time to react to ganks or invades. mobi boots are also very good for heavy ganking, which is what you shoud be doing early game, and also good if there's very few champs with low MR.

First clear guide (raptors regen trick) < this video showed you can healthily clear the entire jungle as evelynn, but you shouldn't do that, you should be heavily pressuring lanes in early game. for first clear you always hit 3 camps (buff, wolves, buff) and gank minute 3. if you can't gank due to lanes being pushed, you invade. there are SEVERAL other routes you can do, but this should work for now.