Rune choices:
Armor Penetration: i like these runes, it's nice to have some armor penetration.

Damage: it's always good to do more damage then you opponent, these runes are great

Cooldown: you want to use you abilitys fast for extra damage.

Armore Penetration Quintessence: same as for Armor Penetration

Masteries

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i have chosen for 23/6/1. why? so you have some DPS masteries in the first. in the second some Magic Resist and armor. and the last for you ghost spell.

(Passive): Renekton uses a new resource system called Fury. Renekton gains Fury by attacking or dealing damage with spells. When he has gathered enough Fury, the resource will be expended to empower his skills with bonus effects. Renekton gains 5 Fury per autoattack. Having sufficient fury empowers Renektons abilities with bonus effects, but this drains Fury. Out of combat, Renekton loses 5 Fury per second. When under 50% health points, Renekton gains double Fury per autoattack making him more deadly.

(Q): Renekton swing his blade, dealing damage to nearby enemies and healing for a portion of the life dealt (more health gained if you hit champions). Fury Bonus: Heal amount raised dramatically. This is your first harassment skill, and it will make you lane longer by healing yourself. Make sure you hit as many champions/minions (max. 5) as possible with this skill in order to gain more health.

(W): Renekton's next attack swings twice, dealing a portion of his weapon damage, stunning his target briefly and applying on-hits each time. Fury Bonus: Renekton's next attack swings three times, dealing a huge portion of his weapon damage, stunning his target greatly and applying on-hits each time (like The Black Cleaver or Madred's Bloodrazor). This is your second harassment skill, your main damage skill, and will therefore be maxed out first.

(E): Renekton dashes forward, dealing physical damage to targets along the way. If he hits a target, he can use Dice for a brief period of time (4 sec) for the same effect. Dice Fury Bonus: Renekton deals 50% increased damage and reduces the armor of units hit. We put a point into this on level 2 for some epic escapes (through thin walls), ganks, and chases.
These are the locations for the twisted treeline, where u can slice/dice through walls.

this are good items if you need to fight mage and dps.
if there are only dps or you just want more damage, you can change Hexdrinker for Infinity Edge
also you can change Last Whisper for Youmuu's Ghostblade

ofc you have to sell Dora'n's Bladewhen you have no space enymore.i mostly need to sell if when i want to buySunfire Cape