I'm planning to write A03

So I'm planning write either fanfiction or original

Here the thing I'm never finished a full on page as full book before only comment. I don't have money either for beta readers, and I suck searching topic, like A03 author has full on Wikipedia information even not found in wiki, and I'm don't keep up with schedule (even though I have full on free time lol)
Also I used to be good in English now I suck at it

So get any tips?