I strongly recommend you don't worry too much about the character(s) for now. The writer of the fantasy novel Eragon and their counterparts, Christopher Paolini, didn't even have a name for his character when he began writing. I believe he just called him 'Tom' or 'Bill', which is unimaginative, but it clearly helped him focus more on the plot/storyline.
Just start writing, deary! Trust me, I know how hard it is when you have writers' block! The really disheartening thing for me to know is: I'm not going to have a masterpiece after a week, and of the twenty pages I write, filled with ridiculous, ineligible nonsense, I only scavenge a mere paragraph or less!
But here's some advice for you, fellow writer:
1. If you have a journal or just some simple scribbles in your notebook, don't throw any of it away! You may very well pull an amazing battle scene or silly kiss session for future use! Or maybe a word or phrase will stick out to you later on! ALWAYS SAVE YOUR WORK.
2. You don't have to necessarily start your story from the beginning. As ridiculous as this sounds, you can start from the middle or end. As you write and grow as a person, you and your story will mold and change over time. Also, don't constantly spell-check yourself! I do it, so don't be me. JUST WRITE, DARNIT!
3. As I mentioned above, don't worry too much about the character. He/She will grow into the story. Think of your story as a brick wall and your character as the ivy on it. As time passes, that ivy will start to encompass the wall. You'll have to be patient with yourself. Someone once related writing to "slicing open a vein and bleeding on paper". As scary as that sounds, it's true: a lot of writers are troubled souls (it's what makes us so sexy). Also, your character doesn't have to be based on someone you know! Well, scratch that... Your character can be YOU, and that's someone you know the best! So, if you don't have one, get a diary/journal.
4. An author I always turn to is Anne Lamott. I frequently recommend her book Bird by Bird to others struggling with writers' block. One of her chapters, Shitty First Drafts, is both hilarious and helpful. In other words, she can give you more advice than I can.
Anyway, I hope to see you on bookshelves in the future, as I love all of the genres you listed!