Six | Phyrexian Altar | Circle of the Land Druid

(and one other card)

Cast
Circle of the Land Druid from your graveyard for its retrace cost by paying ({1} magic symbol) ({G} magic symbol) and discarding a land card.
Skeleton Crew triggers, creating a creature token.
When
Circle of the Land Druid enters the battlefield, its first ability triggers, causing you to mill four cards.
Activate
Phyrexian Altar twice by sacrificing the creature token and
Circle of the Land Druid, adding ({1} magic symbol) ({G} magic symbol) .
When
Circle of the Land Druid dies, its second ability triggers, returning a land card from your graveyard to your hand.
Skeleton Crew triggers, creating a creature token.
Repeat.