Ignite and Flash are perfect for a player who wants to kill and secure the kill. Why I think these spell are perfect are because,
- Ignite secures your kill when u have done a lot of the damage and your prey is running.
- Flash is help full if your prey is running now although you have the Q ability this way even if your target is far you can secure that you will reach it.
- Ignite can also be used when you are dying, so before you are dying try to do as much damage as you can with Ignite.
- Flash helps you to run away if you have a low health and your passive, Blood Well,is on cool down.

The items you pick should be a mixture of attack damage, critical strike and a little of life steal just for some health. If you want you can also use Randuin's Omen for health and defense.

MASTERIES : Try to have a mastery page of mostly attack and a little of defense. Sine Aatrox is and OP kinda guy you should have more of attack.
ABILITIES : First try to have a ranged ability so that you can use it to check any bush is filled with enemies. Since 2 of Aatrox's abilities use health you should learn the 2nd ability Blood Thirst/Blood Price. I would recommend keeping it on Blood Thirst since it would regain your health with every strike.

Now Runes are usually useless until you reach level 30. When you do, try having attack damage, critical attack and attack speed. If you want you can hav some runes of defense and health since he is mostly built up by attack.