How often should I be picking edges? Like, when the first few options show up are they worth picking, or is it better to wait a while and save up your edge points for something better?

How many choices does an average character get, and how often can I expect them to show up as an option?

Do all edges "cost" the same amount of edge points, or are some more expensive to choose?

Are there any edges that I should know about that are extremely important, that most people take?

Any major mistakes to avoid with regard to edges?

Any advice is appreciated as I'm still trying to figure out exactly how this edge thing works.