Going up in [Circle] from [Circle] N-1 to [Circle] N requires N+4 [Talents] at [Rank] of N or higher, at least one of which is a [Circle] N-1 [Talent].

When you go up in [Circle] you may buy one level in a [Stat] without paying the normal [GURPS] double [Point] cost for advancing after [Character Creation]. 

When you go up in [Circle] you also may buy a [Knack] or a level in an [Advantage] if you have the points, and the new ability is relevent and reasonable for the character and the character's [Discipline].