Skarner on ability power(off tank) is really useful bcoz he is dying rly hard and make damage to all enemies around him with RCS you can slow them extremely much.

You need much damage and defense in the beginning. If u want to get fed those are the perfect runes :)

So about the items you got enough damage and defense from the runes so u can start with some speed.After i rush for RoA so I'm sure I wont run out of mana, it gives me hp and damage too so its perfect for Skarner.Choose boots that u think is better in the game.Then I take Sheen for mana and more damage.I dont think ill have to explain for the other items.

Engage by ultying the AD carry and pull it to your team( to make sure she wont survive at low and flash just Ignite him\her)After u do that go for the AP carry.That way the enemy team will focus u and leave AD and AP carry to do damage and the Team Fight is urs :)

I hope I helped u.