How to choose a suitable wedding ring?

Just got back from a search for appropriate wedding ring. I have a headache from what I saw, so many rings. To many rings look beautiful, the main difference is the price.

White gold rings or gold yellow?
14 or 18 Carte diamond?

I’m looking for a nice ring for a gentle woman. So how can you know in advance what she will love and what not? What will fit?

Please advise how to do it right. Is the price of the ring have to mean something to my wife for the future? How much I appreciate her love? Is money invested in the ring that matters?