This Masteries will give you the best possible lane sustain with the most Cooldown reduction as possible.
This also makes you this tanky beast which should be able to put out loads of damage even in a late game.
In the begging when i played Renekton i played acording to the guides and noticed myself that u went squishy and could not put out that much damage in the late game so i started wondering why and soon i noticed that i had way to much health items and thoose damage outputing items which you could need in the mid game to become that beast Renekton really is.

So i started looking in to the builds more to see what i could replace the health item's with i noticed that instead of going a Sunfire cape for the health you instead play the Atma's Impaler earlier instead of later because Renekton has that Natural health from leveling normal so you get the damage you need from the Atma's already in the midgame which makes you crazy.

In the early when you are playing Renekton deepending on whom you are up against try and not to be all to aggressive in the early because as it turns out even if you have the highest Burst damage combo move in the early game, you are still squishy so what i usually do when i play is i try to be as passive as possible and just last hitting to get my farm up homever if they give me an opening to strike you should take your chance and do a harass on them but be cautious your still squishy untill you have the Phage. And you never know who is lurking around in your bushes untill you have wards.

I stick around on the lane untill i have enought money to get me my Ionian's and even the Phage but i usually go b when i have enough money to buy Ionian's and i even buy the Heart of Gold sometimes if i have enough money, it is a really good early item. But if you have the money for the Phage go for it. BTW try and not to forget about stashing some health pots up while your back and fetch wards if you have money over for it. Wards are a priorty but i would not say the 1th because Renekton has such a survability even without them, remember not to use your slice & dice to early because you might spin out of battle and lose the 2nd Spin and that could actually be fatal in some cases so try and remain as focus and calm as possible!

The Runes i have chosen is for the best possible early AND late game, the Armor quints & marks gives you that late game burst while the Seal's & Glyph's gives you that excellent early tankiness =) i am not going to say much about this since you should problably have gotten the point about them now.

The skill Sequence is not that important the only thing i can say about them is that at level 2 it could be a difference in lane sustain depending on if you choose "Slice & Dice" instead of the "Ruthless predator" this ofcourse depends much on what your up against and the jungler they might have.

The Teleport and Flash gives you Exellent lane sustain/escape mechanism's - so on.

Teleport - gives you the best possible lanning for to farm yourself up for the incoming midgame/lategame i highly recommend you picking this althought Exhaust is also an excellent choice!
Flash - even after the nerf on it i still find this more of a use than the Ghost.
Cleanse - is not that good in the classic games, but it is excellent in Dominion as solo bot.
Heal - I have tried heal and i did not find it as good as the Teleport so i would not pick this.
Ignite - i would say that this is completly useless for this kind of Champion. Since the solo mid champion usually or often picks this summoner spell.
Revive - Useless.
Promote - Useless, even in dominion.
Ghost - It could be usefull but id say pick this only if you are going top on Dominion.
Surge - This is not even a AP champ and he does not have much use of attack speed so it's useless.
Rally/Garrison/Fortify - Useless...
Clarivoyance - Do not pick this.
Clarity - You do not have mana.

I hope this guide might come in usefull for thoose who fully understand the champion this is all i have to say i wish you Good Luck :)