Again, here's my simple advice for writers:
Read a lot.
Write a lot.
Publish a lot.
Let's dive into the second axiom: write a lot.
How much is a lot? That depends largely on the writer themselves. Five hundred words for you in a day may be the max, while someone like Brandon Sanderson or Dean Wesley Smith can crank out several thousand. Even Stephen King had, in his definitive book On Writing, said he wrote two thousand words a day, everyday.
Do you have to write two thousand words? Can it be less? Or more?
Again, it depends on you.
My suggestion is to keep track. Either on a piece of paper or on a spreadsheet, write down the number of words you write in a day. One can even use a calendar, then at the end of the week add up the total words in the week.
Keep in mind, each writer is different. Are there days you'll write zero? Of course. Will there be days where you'll crank out two . . . three . . . or even four thousand? Or more? Yes. For me, when I'm on a roll, the words gush out like a tidal wave.
The key to all this is to write as much as you can. I'm a father of three and a husband to a former cancer patient. A lot is on my shoulders. But I still carve out a few minutes here and there to write.