In LLPSI Orberg Scribit: 'Daedalus vero [ad Icarum] ‘Quid iuvat deos invocare’ inquit.
How does the grammar work here? Quid [Interrogative pronoun. Neuter. Nom. Sing] iuvat [it helps] deos [masculine accusative plural] invocare [present infinitive]’ inquit. Does it translate better as: ‘What help is it to invoke the gods?’ or ‘What does it help to invoke the gods’ ?? The sentence seems idiomatic and I can’t quite figure out how it works…though I think I know what it means.
Go with what it means! Absolutely!
If you want to ponder the grammar for its own sake, “invocare deos” is a nominal phrase that is the subject of the sentence.
Iuvat invocare deos. Invoking the gods helps.
Non iuvat invocare deos. Invoking the gods does not help.
Quid iuvat invocare does? What help does it do, invoking the gods?
Latin quid is used in all kinds of idioms that cannot be literally duplicated in English. A very common one, for example, similar to your sentence, is “Quid plura?” “why say more? what good does it do to say more?” 
Another impersonal phrase that’s good to know is “Quid [alicui] refert?” What does it matter? “Non refert.” “It doesn’t matter/isn’t important.”