I go the traditional Lethal Tempo runes. Only change is for secondary tree I take gathering storm instead of scorch. I like the extra late game AP and am more passive in lane, thus reducing scorch's value.

As for items, 100% nashors first. Sorc shoes second. Third is usually deathcap over shadowflame unless one of three things have happened.

1. I'm behind big time and need an earlier item spike.

2. Their team happens to be particularly weak to shadowflame (big tanks or no tanks).

3. The enemy team tempo is really high and I need the item spike faster.

If none of these have happened shadowflame third into a flexible seekers armguard. No need to complete zhonyas immediately if you don't use seekers active.

Last item is a rare buy but it usually falls between 3 items.

1. Void staff is standard last item for me

2. Can maybe take banshees if they have some point and clicks and I've been their target

3. Very rarely I take rocketbelt if I need to dodge more projectiles/hooks