Skarner was my go to jungler at the end of S5 and preseaon.(working with Shen now) what I use to build on Skarner that I had the most fun with was go devourer, rageblade, and then tank.
So a build would be devourer, rageblade, frozen heart, sunfire cape, spirit vissage and boots of lucidity. With 40% CDR it's a non stop Q fest. It to mention if you fight in enemy in the spires circumference, it's over for them.
Another build you can try is Ryalis, rod of ages then full tank since AP also Increases your W.
For runes I went for AS reds, armor yellows, Mr blues and MS quints.
For masteries I think it's up to you, I went thunder lords with 45% CDR and that's fun or go grasp of the undying/strength of the ages route.
I would just keep experimenting with buimda until you fine one that fits your playstyle the best. Right now for example I've been working on a lighting Shen build like how i use to play old Shen. I don't have it down yet but it has potential. One game I went 22/1 and the second one not so much(team miscommunication).
Good luck.
