Actually, if they gave Evelynn a buff, I'm sure things will get out of hand. When I play her even now, she's stupidly strong. I've been playing her back to back in normal for about 2 1/2 weeks now, and I've played 19 games with Evelynn. Out of those 19 games, I've carried about 15 games with her, and I went negative only twice. There was one game where I was completely neutral with a score of 9/9/9. Usually, my score is something like 18/6/16, or 20/7/12. See my attachments for screenies of my recent games with Eve. The only reason why I even got a negative score in the two games that I mentioned was mainly because in the first game that I went negative in, all 3 lanes lost dramatically. I had a great start and was 2/0 for a while, but somehow top, mid, and bot lane all snowballed and so the entire enemy team out-scaled me. In the second game which was last night, I ganked top quite a bit since bot lane fed about 5 kills early game which made Ezreal and Leona untouchable, but somehow top still ended up losing, and our Katarina wasn't doing that great against Lux. Their team ended up out-scaling me as well. Other than that, playing jungle Evelynn is all about constant ganks and tricking your enemy team. One of the funnest things to do is to surprise an enemy and get them so low that they get spooked and flash. Then you can act like you're leaving lane, and if they're stupid enough to stay, you can sneak right back up on them and either get your team first blood, or land first blood.
I tend to start golems with her for its smite benefits, and go red, then wolves. From there depending on how much health you have left, you can either do an early gank, or recall then gank. Eve doesn't really need blue buff to be honest, but it's good to ward blue before going to gank just in case someone tries to counter-jungle. No point in taking red trinket since normal wards can't detect you. =) Also, on most of my junglers, I like taking Ghost instead of flash since it gives you more chase potential, where as flash just positions you closer, or is used for an escape over walls. Evelynn does not need this since she can outrun most champions and then go stealth. Also note that I rather take Skirmishers on Evelyn for the amplified damage + Warrior's Enchant. I then get Boots of Swiftness, and a sheen for Triforce. I also like maxing my E on her rather than spikes. Just be sneaky with Evelynn and you can snowball easily. Plus your Ghost + W + Boots of swiftness + Ult means no one is escaping you, and it makes for a great escape in the middle of the team fight, especially when you're tanky and pop Randuin's Active. If anyone wants advice on Evelynn, just add me.