I don't know. Ceremony looks REALLY good, depending on your reading of "can only benefit from this once" is.
So, state that you really, really like Zog the Half Orc. Because it's +2 AC and saves all day long. He makes you really hard
(also, you can do group marriages. It doesn't say two people, just the people you touch. Seriously one of the best pre-BBEG buffs ever. As long as you can deal with the consequences)
Investiture is a nice way of handing out Hex to people that are mono classed if you're a Cleric/Lock. Great for shooters and extra attack meleers. Only lasts an hour, and takes an hour to do, but still a nice ability to have. It has to be properly prepared, but there's ways of doing that (MI Hex is prepared for instance, while normal Lock slots aren't).
Or just give someone +d4 on ability checks for the next day. This includes initiative checks too.
Seems really good for 25gp and an hour of your time. Sure, you'll have to faff about setting up camp a bit longer, but 24hr non-concentration buffs are pretty rare.
So is it just non-stacking? Or can they only use the listed benefit once during that time period? Or can they only have the spell cast on them with that benefit once in their entire lifetime? All readings are reasonable. I'm pretty sure it's the last one though. Kind of like you don't usually marry the same person twice, it's actually "the thing it says is happening", not just a spell. You are now married, on the cheap, by a priest you know. And you've only got one foreskin, so use it wisely (note: that's not a coming of age thing anywhere really, it happens way earlier. Maybe in tribal Africa?). But by the time you've all come of age, gotten married to each other, and dedicated yourselves to religion, that's about a 2-3 week campaign gone at one casting a day. Then you just never prepare the spell again.
Who says I can't have three wives, two husbands and a pantheistic approach to religion? Elves are weird, and don't seem to consummate enough anyway. Which suits Zog fine.
(you could probably re-fluff the marriage thing as becoming "lifelong battle-brothers" or something if you wanted. It still can only be done once, but it saves Zog wearing a dress. It wouldn't be white anyway......)