Whenever I see questions like this, I know there are going to be a lot of answers about how bad this or that jewelry is, or how traditional rings are evil or a waste of money, or whatever. Luckily I don’t see any anti-marriage replies yet. In any case it’s a good idea to not preemptively use logic and morals to override what your future wife will want and feel.
But this is the right answer. I think if you’re going to get married, it’s good to be at a point in your relationship where you’re talking about these things and you can just choose ring together, or at least discuss if she wants you to be the one who selects it, or if she doesn’t want diamonds, or how much to spend, and whatever else. You should be as confident in choosing a ring you know she’ll like as you are in marrying the person. The best way to do that is to communicate and do it together.