I take attack speed marks to make use of Skarner's passive as much as possible. Armor seals and magic resist glyphs to increase tankiness. Movement speed quints to help with ganks.

I take smite for jungling and to secure dragon and baron. I usually take exhaust to help with ganks before level 6. Exhaust also helps if you get caught while counter jungling. Other useful summoners include Flash and Ghost.

Start with Boots and Health pots. If you don't use smite on blue buff pop a potion when your at about half health. Pop another when stealing their red. Then use the third as you see fit. Kill wolves then blue with the help of mid. If you're up against a slow jungler save smite so you can immediately steal the opposing teams red buff. If he is fast or you aren't feeling that risky, you can steal the wraiths instead. I usually do a typical jungle route after that, getting wraiths then red then golems. Skarner is a great counter jungler, so make sure you are in the opposing teams jungle as much as possible. I usually have mid come with me to steal their blue around 7 minutes in, I take it then give our blue to our mid. Focus on counter jungling until lvl 6 and then gank like crazy using your ult.

I start with boots and health pots to increase sustainability and movement early in the jungle. I think it really helps with counter jungling early. After that I usually either get sheen or heart of gold. Sheen for damage and Heart of gold for survivability and the GP5. Next I usually get a sunfire cape for the armor and health. Wits end is really nice because it increases damage, magic resist, and attack speed to really utilize his passive. After wits end I either get Guardians angel or Force of Nature. If the other team is AP heavy I go with FoN for the high MR and increase in movement speed. To finish out your build finish your Randuins and Trinity force. If the game lasts this long and you finish the build you should do a lot of damage and be pretty hard to kill.

I've tried a few different builds with jungle Skarner, and I like this the best. It has enough damage, but keeps you tanky enough that you can initiate like you're supposed to. Please comment and let me know what you think or how this build could be improved.