If you remember, the original YGO had a "ranking system" set out by Kaiba Corp, which spelt out skill through stars. Now, these "stars" are more to point out the level of the character your currently playing as, dueling and deck forming. At the moment they don't mean anything, but might later in days to come (such as the option to get certain cards and other such things, like 'omgwtf' Runners and ect)
Currently, I am writing up a long explanation about this system for the database. For now, it's pretty simple.
Edit: Those who do not have stars may ask for them here in the thread. My own stars of my current main character (Kai) are set at "Three" until others decide on a better ranking, lower or higher.