Katarina is a great carry. She is able to do high damage in early, mid and late game, she also has great sustain and survivability because of her skills. The most important feature is that she is very fun to play.

Pros:
-High damage and nuke;
-Can carry the game;
-Natural flash;
-Fun.

Cons:
-You must be careful with disables.

Well, Katarina is a great carry on dominion, due to the fact she can spam alot of skills.
Flat AP Quint. and AP/P Lvl Seals and Glyphs and Magic Penetration Marks are also great choices.
Why use AP/P Lvl runes?
-You reach higher levels in a few amount of minutes, so they're the better choice.

Why use Flat Ap quint?
-The difference of Flat / Per level runes are small.

There are not much options for Katarina...
Go full AP tree and some sustain on early game.

This build will give you high sustain in lane, high damage, and high survivability

[*] Sorcerer Shoes - > Huge M/PEN;
[*] Rabadon's Death Cape - > High Damage;
[*] Rylai's Crystal Scepter - > It will give you some survivability and slow;
[*] Will of The ancients or Hextech GunBlade - > It will give you sustain in teamfights and some damage;
[*] Quicksilver Sash - > Anti CC, perfect when their team has to much disables;
[*] Abyssal Scepter - > Stacking with your boots, it will give you almost true damage to their carry's;
[*] Zhonya's Hourglass - > It will give you some vital time to stay alive and leave the team fight when necessary.

Depending on enemy team:
If they have to much disables: ALWAYS build QSS and Zhonya's for survivability;
If they have no disables: Go full ap build and rush Rabadon's and Rylai's, and feel free to rule the game.

Recommended:

- It will give you some escape from melee enemys. Katarina already has a "natural flash", so two are better than one, and these choices also provide that last little bit of damage to take the kill.


Another Options:

- Ghost is more frequently used in Dominion, as it can provide you speed to defend the point or capture the point while your enemy is dead, and the ignite can take the kill for you.

- It will provide you some defense against AD's and some damage against them.

Why maxing Shunpo?
- Shunpo is Katarina's secret key, as you can use to slay you enemy ,or to escape from death.

Why take Killer Instinct only at lvl 13?
- Killer Instinct is not as useful on Dominion as Bouncing Blade.

Why don't max Bouncing Blade on first?
- It's not as useful to max, because the enemy walking in groups is not a feature in Dominions early to mid game and shunpo has more forceful, deadly burst.

On early game:

Step 1 + + It will probably grant you the kill.


After reached level 6:

Step 2+ +
It may probably used when there is more than one enemy, if u took the kill repeat the Step 1


Late Game:

Step 3 + + + +
Death Lotus will probably kill everyone on teamfight, if you kill one person, repeat Step 1, if you kill two people, repeat the 2nd step.

During those Steps, you can use, when necessary and/or and/or for survivability.


Also note: Use of Smart Cast is extremely recommended.

Rush the middle point, then go to the top point, have a good position. When the enemy becomes to have mid/low health go ahead and kill him/her/them.
Then Safely capture the point.

Your enemies can't kill you, just take their points, and if someone tries to capture the point, just kill them and defend the points.

The perfect team for Katarina: Alot of AOE and disables;
The worst team for Katarina: tanks only;
How to deal with it: She needs her team to take the CC's for her, if she has QSS she can deal with it herself.
Katarina is ALWAYS focused, so you need to have great positioning and patience for mistakes usually result in disaster.