Copied and pasted from reddit

When you are asked, in your opening sequence, "Why did you become an adventurer?" you are given four options. Each starts you with a ring that you can find in your Armoury Chest (Ctrl+i):

To gain power. : Ring of Fortitude (Critical Hit Rating +1)
To win glory. : Ring of Fidelity (Vitality +1)
To amass a fortune. : Ring of Fortune (CP +5)
… : Ring of Freedom (Determination +1)

All of the rings also have the following characteristics in addition to the above (most of these are typical, of course, but I'm including it for completeness' sake):

Defense : 1
Magic Defense : 1
Condition : 100%
Spiritbond : 0%
Repair Level : Goldsmith Lv. 1
Materials : Fragment of Grade 1 Dark Matter
Quick Repairs : 10 Gil
Non-convertible
Sells for 6 gil

Since I haven't seen this mentioned it so far, I thought it would be nice to point out for others' sakes. This ring isn't bound to your character, either, so if you have a friend, they can start a new character and give you the ring, allowing you to start with two rings right from the get-go!

The best one in the long run is the Ring of Fortune. If you're not restarting multiple times, go for that then. If you are, I suggest you restart 4 times, getting 2 rings of Fortune and 2 whatever you want.

agreed, +5 CP is pretty huge at early levels

Yes, because the next CP ring is at late teens. Personally, i'll get all of them since I have 2 beta accounts…. hahahahahahahha