I promise the worry and panic when you first got your navels pierced is normal.
But I do feel it is important to invest in a good navel ring, rather than purchasing navel rings made of cheap metal. My skin is extremely sensitive, so I'm wearing a navel ring of high grade metal. I believe surgical steels are fine and if I remember correctly, I am wearing a titanium one.
Here's a quick picture update, I apologise for the low quality as I zoomed and cropped my images:
Personally, the belly ring serves absolutely NO inconvenience, I wear it when I lift (with a lifting belt) and there's no discomfort or pain. Even when doing abs exercises which involves a hell lot of crunching, there's absolutely no discomfort at all! Oh yes I've gone swimming too in usual pools and the sea, and it has got no effect on the piercing. Simply just bathe as per usual and you're good.
So if you need any help deciding whether or not to get it because you're worried it might pose as an inconvenience when doing any sorts of sports, trust me and just go ahead with it! If anything, it's a beautiful accessory to have on your body. I've never once regretted this piercing, it's my favourite out of all my 7 piercings!