Hello guys, Mansgar here.
Please note that this is my first guide ever, so please feel free to leave a comment of your oppinion. I won't be keeping you busy with my pladder so I'll just go through the basics.
Graves is a great carry at the moment, probably the best one and this is how I build him.

Summoner Spells: Now that heal is boosted it's a really smart idea to use it for carries and flash is exeptional for chase and escape. I really can't recommend any other summoners.

Masterys: I build Graves super offensively, wich you should on a ranged AD carry. You're the main damage output. Let's start with offence. You really want to have the left side of the offence tree because it's alot of great stuffs there for Graves, take Lethality or Sunder for example. I really recommend that you build this in the offence tree. I use this build in utility because I don't really waste alot of mana in lane, but if you do, the extra mana and mana regeneration is a good idea. If you want to get extra mana and mana regeneration, I recommend: 1 point in Summoner's Insight and 1 in Improved Recall. Then grab 3 points in Expanded Mind and Meditation and top it off with one point in Runic Affinity.
Tho, if you're a person that likes defence, go 21-9-0 and grab 3 points in Hardiness, 1 point in Resistance, 4 in Durability and 1 in Veteran's Scars.

Skill Sequence: You really want to spec in Buckshot since it's your main damage ability and it's also exeptional for farm. Smoke Screen are just one of those "good to have abilities" that you don't really spec in. After Buckshot I spec Quickdraw for the attackspeed and lower CD.

Rune Build: I can't really recommend anything other than Greater Mark of Desolation because it wears down the apponents armor and it's extremly helpful through the entire game.
In seals I normally use Greater Seal of Resilience because I don't waste alot of mana in lane. But if you do and don't have a Soraka support with you, use Replenishment instead.
In glyphs I normally use Greater Glyph of Warding instead of Focus because Graves does'nt really have abilities with high CD's and in my oppinion, MR is more inportant.
In Quintessence I use Greater Quintessence of Desolation because I like to wear down the apponents armor and I think it's more useful, but Strength works just as well.

Item Purchases: This build is, according to me, the best "all-around" build. Of course, I don't use this build all the time. It's really dependant. If I have a Soraka with me or know that I have the offencive lane I start with Dorans Blade instead of Boots because I won't take as much damage and sometimes it's best not to buy alot of Doran's Blades and Wriggle's Lantern and just go straight to Bloodthirster.
I hope you noticed that it's alot of items there and you can only use 6. Explanation? Sure. The Doran's Blades should be sold after about 15-20 minutes beacuse they're not really useful after this time. If the game is really long and I have my 6 items, I sell the Wriggle's Lantern and buy Bloodthirster.
If I'm up against a team that includes Warwick or Malzahar for example I like to build Quicksilver Sash instead of Banshee's Veil, and much earlier. The reason I'm doing this is that Warwick and Malzahar likes to use their ultimates on the Carry, wich is you and that suppress is really annoying and you won't be useful in teamfights. Quicksilver Sash will remove the suppress.

Graves is probably my favourite champion at the moment. He's just such a bully in lane and really useful in teamfights. He's got the damage (OH THE DAMAGE), he's got the escape/chase and he's got the slow. Graves is a great champion and I really don't hope he gets nerfed.
Please leave a comment of how you guys think I did in this guide and if you have any tips for me.
Best regars, Mansgar.