I buy elixirs often in game because of the extra boost in health early in the game but start with doran's shield because it lets you lane for forever then go back with 1300 gold and buy hi-tech revolver which gives you cheap spell vamp if you have enough buy a health elixir then when you come back again buy a quick needlessly large rod for the large amount of ap then buy a rylai's staff for the survivability then follow the guild as proceeds.

As for the runes i like a little ap and survivability early game for in lane ganks and first time ult usage.

With masteries i prefer a tanky set up to let you stay in lanes for a while until you get 1300 gold also it is very important for katarina's ult giving her more health plus she doesn't need mana masteries because.... well she doesn't have mana.

I prefer maxing out bouncing blades for farming and mid lane harassment early to mid game but many go with shunpo.

For combos i think that someone with a heavy stun of a suppressing ult is good to lane with if you want to solo have a ww jump in to your lane and ult an enemy champ then you shunpo in and ult as well practically insuring a kill. I also like laning with Galio,Taric,Sion,Amumu, or any other AOE stun or heavy stun.