Fictional Character

I'm not entirely sure about the specific details of my fictional blog character. I'm pretty sure I want to write the blog in first person, because it really allows you to get in a character's head. I'm tempted to make my character a man, simply because I think it would be a challenge, but I'm not sure I could pull it off. So, right now, the potential names for my character are Calvin or Callie. I'm wondering how far in depth I should go in writing the character, since I'm not sure what story context the character will have to exist in yet. Should I just brainstorm personality traits and a brief history?