Firstly, Mazal Tov! May you and your groom merit to build a “Bayit Ne'eman b'Yisrael” – a beautiful Jewish home. And may God bless you with many, many years of health, contentment and continued growth together.
The accepted custom is to use a ring made of either gold or silver. It should be plain and without any kind of a stone so there should be no doubt about its approximate value. There is a Kabbalistic idea that the ring should be plain, without engraving and design. The reason is that a smooth ring is symbolic of a smooth trouble free cycle of life.
Disclaimer: In all matters that deal with a wedding ceremony or a synagogue service, anything I write is based on sources and customs that I am aware of, but I must stress that the final decision in these matters should be made by the Rabbi who officiates the wedding or is the Rabbi of the synagogue.
