This current build is a work in progress but is currently how i'm playing renekton, it's very effective due to its immense versility. Renekton is an amazing adaptible champion due to his no need for mana, the only thing he needs to be effective is cooldown reduction. My current problems with "Rene" is his squishy-ness early, thus why I use defensive masteries and build resistence early depending on what the enemy team composition is.

My current order of items is based on gold income, I get a Heart of Gold and a Avarice Blade + dorans shield and Ionian "CDR" boots. This mixed with your ability to farm is just amazing for building gold income. I sell the Doran's Shield next and get a Spirit Visage for more CDR and health. Then I sell one Heart of Gold and get either a BF sword or a brutiliser, depending on if I needed to back early or not. The rest is pretty much how you want it.

The first 4 items are really the core, the last two are optional. Start with a Doran's Shield. I deffinitly prefer "resistence" boots IE; Dodge/MR over the CDR ones since you hit the 40% cap nearly with the core items anyway BUT if nessercery take the CDR boots and then replace them later after your core build.

The optional items can be pretty much any decent combo; farming well? Bloodthristers and Black cleaver are OP late game on Rene. I am mostly running Black cleaver. You can littrally hit your end of your core items at around the 25-30 minute mark at which point you assess what you need and fill the last two spots with them.

When engaging in team fights follow this set rule; E into pack. Pop Ranudins followed by Dominus. Hit Q followed by W onto the focused squishy. Pop Ghostblade and UNLEASH HELL!... Once Ghost blade is dead access if you can chase or need to back. If you can chase someone down, hit ghost and chase them into exhaust range... hit exhaust and again use your combo (remember you can E twice if you hit minions).

When being engaged in team fights Pop Dominus followed by Ranudins. W the tank and Exhaust the carry. Then Q, Ghostblade and attack the enemy carrys OR back and cover your carrys as best you can.