How does “Reputation” work?
When I reached 200 reputation points last week, I got a bonus of 100 from Stack Overflow, and I searched to know more about when and how these point appear, but no luck. When do you get freebies?
Basically, you get a 100 reputation "association bonus" when you link your account with another Stack Exchange site and at least one of your accounts has a reputation of at least 200.
you associate accounts of two or more Stack Exchange network sites, and at least one of those accounts already has 200 or more reputation: +100 on each site (awarded a maximum of one time per site)
There really are no more freebies other than this. The 100 reputation association bonus is really just to allow you to skip past all of the new user restrictions, as it's assumed that if you have at least 200 reputation on a single Stack Exchange site, you've already begun to learn how the sites work.
From this point on, for any Stack Exchange account you create on any of the Stack Exchange sites, you'll start out at 101 reputation.