Creative, alluring and interesting, the belly button a.k.a. navel piercing can be adorned with a variety of jewelry designs.
The classic jewelry choice for this type of body piercing is a 14g curved barbell featuring either gemstones or opals. Normally the bottom ball is larger in diameter than the top. This is not only inviting to the eye, but also comfortable.
If you have a double belly button piercing (the top and bottom) you can use a traditional belly button ring in both or choose to wear a 14g curved bar in the lower one with flat gemstone or opal ends.
If you have more of a "floating navel" style piercing of the belly, your jewelry choices may be different than the traditional belly button curved barbell.
Some people choose to wear more of a "J" curved style barbell (combination of a curved and straight shaft) or a 14g curved barbell featuring a ball, gem or opal on the bottom and a cluster piece on top.
Individual aesthetic preferences and body piercing angle and depth contribute to the choice, especially in the floating navel style.
Over time, you'll find what makes you the most happy. Sometimes it takes a few body jewelry styles to lead the way.