Graves is a pretty easy champ but the main mechanics you want to learn is the fast auto e cancel and how reload canceling works. There is a distinct animation that Graves will enter after spending a shell, during this animation you can freely cancel the e animation with any ability which allows you to reach terrain with q from longer ranges and surprise people with Q angles under tower. A common tower dive pattern at six is after conditioning them to stand to the side or inner side of turret you can enter reload animation E > Q > flash > auto > ignite > R to kill most squishies at around half health on dirk while only taking one tower shot. The fast auto E cancel just makes your next E come off cooldown faster by E'ing as the pellets are still in travel time which makes them count towards your next E cd reduction. Another mechanic that is key to managing mana is learning how pellets will spread off of last hitting a minion, you only need one pellet to count towards pom/conq and using this ofter is key to using the conquror playstyle properly.

Graves is balanced around being in the jungle with limited resources, but with lane Graves that limitation doesn't exist, being able to funnel plates, minions, and camps will usually easily let you carry as Graves scales with ad and his item interactions rather than snowballing off of depriving resources, this often means you will outscale champs and hit powerspikes faster just by farming better. Fortunately this is very easy to do as you should be averaging 9 to 10 cspm every game while also holding priority in almost every lane you are in, this is amplified mid where it's easier to take raptors and set up dives in the side lane.

Graves can easily solo carry games and abuses lack of vision very easily. Graves can fit many comps due to his build utility but your main goal is snowball into the late game. KDA doesn't matter as long as you can abuse the points where you are stronger than the enemy laner, and being weaker than the enemy laner doesn't matter if you can scale to where you are stronger. Graves only gets stronger as the game goes longer but usually your priority in fights will be blowing up and dumping as much damage as possible onto the backline in any way possible.