If i have a cithria at base and i play a ablus ferros can i spent the buff cithria will get from playing another unit?

Yes. When you play Albus Ferros, both triggers go on the Chain at the same time — Cithria's "when you play another unit, buff me" and Albus's "when you play me, spend any number of buffs." Since you control both, you order them so Cithria's resolves first, putting a buff on her, then Albus's spends that buff to channel a rune.

This is confirmed by FAQ 7766: stack the play effects, resolve Cithria's buff first, then spend it for Albus's effect. Just remember Cithria has to be on the board before Albus is played (she doesn't buff herself when played alone), and she'll only have that one buff to spend since a unit can only hold one at a time.