You have basically to activate Necrovalley and Spiritualist as soon as possible. You use Supernaturalist effect in order to add Necrovalley Throne (or Imperial Tombs if you already have Throne in hand) in EP. Next turn you just use Throne to add Gravekeeper's Headman, and use Headman's effect in order to summon Spiritualist again. You can now summon another Supernaturalist or link summon Verte Anaconda, in order to get Dragoon or Starving Venom Fusion Dragon, using SuperPoly.
I added Malefic Stardust Dragon cause it protects Necrovalley, and you can use it to summon Anaconda. Double Summon is also for Anaconda. If you have Recruiter on the field you can summon Artemis, triggering its effect. So you can add Commandant (in case you don't have Necrovalley on the field) or Spiritualist. Summon Black Rose Dragon (with Ash) if you want to clean the field. There's no Royal Tribute cause it's good only if you draw it in turn one imho, but you can add it in Side. SuperPolys and Storming Mirror Force in Side are for Dragoon.
I think this is the best Gravekeeper's deck ever built. Even if it's still a really slow-paced deck, it's a good antimeta, and it's also pretty simple to play.