What type of nose ring to buy?

I just got my nose pierced and now I'm starting to look at new rings... I have a few questions, though... First off how do I know what gauge to choose? I don't know what I was originally pierced with. Second...what's the difference between the left and right nostril rings? Third, I saw a ring I liked and it said it's made of solid titanium...but is that safe to put in your nose? It was the only titanium one I saw on the site.