In Malachi 3:17 God describes His people as being His 'jewels.' In other words, we adorn Him. But a jewel doesn't need adornment. A jewel sparkles due its own character as a jewel. I don't know what you mean by 'compulsory.' At our assembly we believe that the only thing that God accepts is free-will offerings. So even though we believe Spirit-filled believers only obstruct the holy sparkle by wearing jewelry, we would tell you that if you have your heart set on bedecking yourself with jewels, whether real or fake, far be it from us to tell you that you can't.