FB is handy for two things.
1.) A fake FB account that allows you to login to millions of websites via your FB account without the need to establish an individual account local to each website. Associate the fake FB account with a real, but throwaway email account used for no other purpose. Never use your fake account for anything but that. Lie about all demographic data when you set up the fake account.
2. A real one where friends and family can find you. At a minimum, lie about your birthday. Never post anything personal about yourself or anyone you care about on the real account as all posts are being mined by FB and the government.