Though I see most people staring by making a character. Which is usually the main one. Generally the page starts simple but develops over time when you start to flesh it out and whatnot. As long as page follows guidlines of course. Has feats and whatnot (Which it seems you do have already so that shouldn't be an issue) and proper format, then it should be fine. But that's just one option. You can also create a verse page and stuff which develops in a similar fashion. Really, it's up to you, but I will say I'd be more than happy to give critiques and such to help~
Also I didn't answer the other question but I suppose the most difficult part for me was making the characters' backstory and defining their powers. Also making such things related can be a pretty complex task so I'll say thats what I had troubles with.