Graves is an attack damage carry or ADC. He has an extremely strong laning phase and is fairly easy to use. When mastered he can destroy any team or opposing adc. I am not a pro as unless you are then a pro build would not suit you for your elos playstyle most likely. This is probably not the best build possible but I have played graves for around 100 games and this is what works for my style of play. If you feel you want to add your opinion then leave a comment and like/dislike so I can improve upon this. Don't leave troll comments as those won't help others do what they came to do.
So more about Graves. He is my favorite ADC overall as he is never weak. His laning phase rivals that of Draven and late game is almost as good as vayne's. He is a popular champion that can counter other common adcs such as Ezreal, Kog Maw, and many others. He has few weaknesses except for his lack of great escape abilities such as tristana's or ezreals. He has fairly good burst and has great early game damage with his Q. Overall this makes him my favorite ADC.
I ntend to improve this greatly as it is my first guide. Im a noob atm so dont hate.
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-Pros
Strong All Game
Great Teamfight Damage
Wave Clears and farming are Easy
Counters Most Adcs and can rid of their field of vision in Teamfights

-Cons
Bad Dueling
Low Damage To Tanks
Caitlin can be a hard counter but is the only one imo

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The masteries are fairly simple. Take 21 points in offense and preferably 9 in defense. Get Veteran's
Scars and put 3 in hardiness. The points in offense are simply all the damage culminating in Executioner. You can make variations dependent upon preference.

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I Tend to max Q as fast as possible and neglect the w for a while. This is mainly due to my playstyle as normally w isnt needed till around lvl 9 unless you are laning ezreal. However it is good for zoning as they cant cs and are disoriented(especially if they are scared of the dark). I find the Qs damage with a high cc support to be a bit too stronk but if you have a sona/soraka then w may be needed to extend the zoning. I max e second as the attack speed is helpful if you start with 2 pure dmg items.

Flash and ignite unless you are against a team that you feel cleanse will be effective against. Heal and exhaust are also not bad if your support or you wants both. Other than that I feel the others are not as helpful unless it fits you playstyle.

Getting farm with graves is fairly simple with a dorans blade. You can be aggressive early game to varying degrees dependent upon their team comp. (ex. Shaco play passive/let them be lead lane. WW or any other bad early gankers you push and lose them cs to turret). Try to hit around 100 cs by 12-15 minutes dependent upon your aggressiveness. You should easily out cs them unless they have a Caitlin or good laners. Make sure you out cs their adc all game and if you can, their whole team.