Use Gravekeeper's Recruiter to tribute summon into Gravekeeper's Chief, then use Gravekeeper's Chief to revive Gravekeeper's Recruiter, While Gravekeeper's Reccruiter searches your deck. This combo is an instant +1 for you, and can be improved and made more consistent by adding Enemy Controller to the mix. Use Enemy Controller and tribute Gravekeeper's Recruiter to take your opponent's monster, then use Gravekeeper's Recruiter to search for Gravekeeper's Chief. Tribute the controlled monster to summon Gravekeeper's Chief then Revive Gravekeeper' Recruiter. Not only is this Combo a +1 for you, but it also serves as monster removal.
Can this card be used to bring out Oracle (2000 attack) and visionary (1900 attack)? Someone in a ranked duel did that to me and both of his recruiters were prismatic so I'm already suspicious of cheating.
If you had READ gravekeeper recruiter's effect properly AND also READ Oracle's DEFENSE stat properly, you'd know that it's possible.
Gravekeeper's Visionary is not in the game yet. You're probably thinking of gravekeeper's chief since you were mentioning 1900 attack. Both cases are possible since they have 1500 defense.