Avremmo dovuto provare per saperlo! Bastava ce l'avesse fatta uno solo di noi.
Given the use of the past conditional "avremmo dovuto" in the preceding sentence, I assume that they are talking about a past (conditional) event that actually didn't take place:
They wanted to try doing something but couldn't – they should have – and it would have been enough if just one of them had done it / succeeded.
When the verb "bastare" is involved, do you usually use the combination of Indicativo Imperfetto "bastava" and Congiuntivo Imperfetto "avesse fatta" like this to convey a past conditional meaning?
Incidentally, could it be that "ce" in "Bastava ce" is a colloquial or regional variant of "che" used to introduce a subordinate clause?