If you think 3 failed persuasion is bad, I failed most of my persuasions, that's like 11 chapters each.
Persuasion Rate is about 5-10%.
Statues? You can't even get anything above Rare + for them. Not worth it ONE BIT. I bought several, and am currently pissed off to no end for doing so; I'm saving them for 4 star pirates that I'll meet sooner or later.
If you're going to spend gold on cards, wait for the event cards, that often have the same price as the regular gold rescue, but has a very decent (~10%) chance of SRs, or even SR+, on rare occasions (Cheerleader).
Not only does the event rescues have cards that help you in the event (CAPTAIN OBVIOUS) to assist you in getting those event SRs, but even after the event is over, they usually have some kind of skill (along with high stats in general), that assists you even further.