Lands you control can tap to produce at least ({4} magic symbol) ({U} magic symbol) ({U} magic symbol) ({U} magic symbol) .
Steps
Activate any number of lands you control by tapping them, adding at least ({4} magic symbol) ({U} magic symbol) ({U} magic symbol) ({U} magic symbol) .
Cast
Turnabout by paying ({2} magic symbol) ({U} magic symbol) ({U} magic symbol) , untapping all lands you control.
Donnie & April enter the battlefield, they trigger, returning
Turnabout and
Ghostly Flicker from your graveyard to your hand.
Repeat.
Notes
If lands you control can tap to produce at least ({5} magic symbol) ({U} magic symbol) ({U} magic symbol) ({U} magic symbol) , this combo nets infinite mana. You can then stop casting
Turnabout and blink one other permanent using
Ghostly Flicker. You may also tap artifacts and/or creatures instead for mana if desired.