These are the masteries I use for Graves. I use a 22/0/8 mastery build typically. Another mastery set up is 21/9/0 in order to make Graves tanky and beefy.
For runes I use a standard set up for ranged AD. Armor Penetration Marks, Physical Damage Quintessences, Armor Seals, and Magic Resist Glyphs.
Skill Order 1-6:
I use Flash/Exhaust for summoner spells or Flash/Ignite if I want to play an aggressive Graves. If bot lane and the rest of their team has a good amount of CC or I want to counter exhaust, then I run Flash/Cleanse as Cleanse now removes exhaust.
These are the items I would have by end game for Graves in a situation where I can just go all out damage output. However, this is very rare and far between. In replacement of one of the Phantom Dancers, I build a Quicksilver Sash or a Guardian Angel. Usually I am building a Quicksilver Sash as this allows me to cleanse and use QSS if cleanse is on cool down.
I start off with a Doran’s Blade then on first return I buy boots and another Doran’s Blade if I need more health and don’t have much money for anything else. I never go past 2 Doran’s Blade in my item build though, this should only be done if you feel you are extremely far behind you opponent. I farm until I can go back and buy a BF Sword, which I then turn into a Bloodthirster, followed by a Zeal into a Phantom Dancer. Then I build Infinity Edge and Last Whisper. If the enemy team is lacking in armor then I quickly grab Quicksilver Sash or Guardian Angel instead before finishing my build with a Last Whisper. These items make you durable and do a ton of damage when you Q and E.
During the laning phase you want to just farm as much as possible. Hopefully your support will harass and deal with the trades. But if not or when you see an opportunity without losing the trade, harass and damage your opponent. This causes them to be denied money from CSing as they have to back away. This gives you some free time to farm and get even more deadly. When you are laning if you see the opportunity don’t be afraid to charge into your opponent with E followed by your Q. This allows you to get some auto attacks off if they run with your boosted attack speed after they take the burst damage from your Q. Graves does a lot of upfront damage when closer to your opponents. This make perfect sense as he is using a shotgun as his weapon of choice. Now with that said, you should try to damage you opponents or farm with your Q as it clears waves quickly and deals a fair amount of damage. A good way to burst someone down with no armor comes around when you hit level 6. When you get your ultimate try and keep your opponent fairly wounded, say around 70% or less. If you can close the gap with your E, then follow up with a chunk of burst damage from your Q followed by your ultimate. That champion is pretty much a guaranteed kill, unless they have high armor values, which most champions do not bottom lane. If they don’t die in that combo, then auto attack them and they will surely die.