Fun fact, diamond rings only became a thing back in the 1940s when a diamond company pushed an ad campaign that, to paraphrase, said 'she can't say no if you propose with one of our diamond rings'.
The ring itself is also not necessary, it's pomp and circumstance. Whether secular or Christian, what matters in a marriage is that it's properly officiated (either by the state or under the eyes of God if that's your thing) and that both parties want in.
Also, genuine attraction and commonality helps, but if you're getting bound in matrimony that's probably something I'd say should be a requirement, else misery tends to follow swiftly after.
On my side, we got married back in 2013. Small affair, only direct family. Apparently weddings like that are statistically more likely to produce happy marriages, who'da thunk? We drifted apart on good terms years later and still meet up for drinks now and then. Probably one of the better relationships I can claim to have had.