Just add fields to your profile categories as they come to your mind. If you want to change the order of these fields later on, you can always do that via drag&drop. You can even drag fields into another category if you wish so.
To reposition the categories themselves, click the "Move category" button, reorder the categories and click "Finish moving".
The order of the fields in this admin view will be reflected by the order in the actual user profile.