Y'know, I'm a fan of the ambiguous OC, but that entire concept was my creation to begin with. I'm going to do bullet points for this because I have a lot to say. Hope you're prepared to do some reading!
- I'm not going to criticize you for doing a self insert because I did them myself when I was younger. But when I started to get serious about my craft as a writer, I stopped doing them. The best way to showcase an artist or celebrity that you like it to make sure that the spotlight stays on them. Otherwise the OC begins to turn into a Mary Sue, and nobody wants to see a Mary Sue.
- As someone who started out about your age in the fan fiction world, a piece of sage advice. Notice how things are written in books, try to replicate that. Find your own voice but try to keep it formal unless the plot requires the narrator to be otherwise.
- Use grammar check and spell check, and use them often. Take the corrections they both suggest. Poor grammar and poor spelling take the focus off your plot, where it should be. You never--EVER--want a reader's focus to be anywhere besides the plot, because that means they likely won't finish reading, and all your hard work was for nothing.
- Most of all, remember this. Unless it's just outright senseless hate, like "you fucking suck, stop writing!", it's not a flame. Constructive criticism is something you are always going to be receiving if you plan to do this professionally. When you submit a manuscript for review by an agent, it will get criticism. Editing it to suit that criticism will be like butchering your firstborn child, but trust me, it's worth it. After you get an agent to represent your work, and a publisher accepts your manuscript, it will go to an editor, who will go through with a red pencil and butcher your work again, and ask you to make the recommended corrections. Revision is necessary to bring forth your best work.
Take it from someone who's been where you are, kiddo. You don't wanna give up just because you hear things you don't like, okay?