I find you can get away with playing him AD or AP as long as you have a tank item or two to actually survive your engage.
Skarner will always be an AP bruiser for me, so I build him differently from other players. His new passive supports high AD which is why many players run Trinity Force and this is a good idea if you want high damage output.
For me, Skarner is a team-reliant, heavy engager who zips past front line, grabs the back line and pulls them to his allies. So my build is different from what people like since I build high AP.
Why do I build high AP? Skarner's shield (Crystalline Exoskeleton), upon which his speed relies, has an 80% AP scaling ratio. Having 200 AP gives you a 160 HP shield and speed to bust through to the squishies. Throw down Fracture, which also scales off AP, and slam them with a Crystal Slash to get a minimum of 2 stacks of Crystal Venom on the target.
Now you hit them with your ult. They take an extra 400 damage from the venom stacks (200 at the beginning and end of the suppression) and now you can use that speed and shield to safely drag them to your laner(s). This works exceptionally well when engaging from the river. There is nothing more rewarding than grabbing the enemy carry and 'introducing' them to your turret.
I like the Blasting Smite from the Ranger Trailblazer. Skarner already has excellent clear time once he hits level 3, but blasting smite just makes the jungle that much safer for him (first clear is still a bitch). I take Q,W,E at 1,2,3 in that order. Having E in the jungle give you an initiating stack of venom from a distance so you can get your stun off quicker and prevent some nasty damage. It's a toss up after that - I level Q and W together but you can put your second rank in your favorite one first - I prefer the shield. you might prefer the damage.
Depending on enemy composition I prefer the tank items Sunfire Cape and Spirit Visage. You really do need at least one tank item now that you cannot reduce the cooldown on Crystalline Exoskeleton by attacking.
Besides the jungle item, which is up to personal playstyle preference, my build will often look like this:
I am by no means recommending this build. This is my build which caters to my playstyle.
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I also run hybrid runes which grant Armor (seals), Magic Resistance (Glyphs), AD (Marks), and AP (Marks), and Cooldown per level (Quintessences). This gives me early beefiness against both AD and AP, and allows me to dish out significantly more damage at level 1 with Q. I can get my shield up very quickly at 18.