Carry every game
Against all AD
Against healing teams
Every game at level 9
Not Updated For Current Season
When playing Graves, you should prioritize counterganking, farming, and counterjungling. You should strive to be the highest level in the game with the most gold, but don't AFK farm. Be there for your team when you can turn a fight around. Because you're Graves, you should be able to win most 2v2s when counterganking, which puts the enemy jungler behind and you significantly ahead if you get a kill or three.
If you can't gank for a guaranteed kill or flash (gank these lanes again for a kill), just farm or counterjungle. You can 1v1 most enemy junglers by keeping your E at 3-4 stacks while in their jungle. You can auto scuttle crab and use your W on camps to keep your E stacked longer. If you can 1v1 the enemy jungler, you should invade them and create an even larger gold gap. Deny every buff, never let them get a camp, ward their jungle. Watch out for collapses from the enemy team, unless you know what fights you can and can't get away with you can accidentally feed a shutdown or bait your team into a bad fight. This comes with experience, and you'll learn what Graves can do as you play him more.
On Thunderlord's and armor penetration
The Thunderlord's and armor penetration build may do tons of damage, but the items and masteries offer little to no defensive stats and make it very hard to reliably carry teams with a weak frontline. Running SotA and items like Phantom Dancer and Death's Dance let you do all the heavy lifting for your team and gives more consistent results in SoloQ.
You can watch Tarzaned stream Challenger jungle gameplay live at https://www.twitch.tv/tarzaned