As a writer and editor, there's one peculiar trend I have noticed over many, many years. It's in keeping with the great tradition of capitalism that the higher you rise, the less you do.
I'm not indicting this trend. I'm just observing that it may exist - and that new writers can expect it.
The less you make, the more you're expected to crank out.
It may follow that the more you're expected to crank out, the less quality you produce. And then the fewer clip book quality pieces you have for your portfolio.
That said, the better you are, the more solid every word you write is - and the less editing it requires. This involves not just practice but talent - and watching carefully to see what can be done (and what IS done by editors) to improve your work. If you don't watch how your copy gets better between your computer and the printed page, you won't learn from it.
So, the better you are, the better stories you're assigned - and the better your clip book will look, too. And the better opportunities, and the better pay you will get (although the difference between what a good writer and a mediocre writer is paid at a smaller publication is not that great, since good writers are underpaid at smaller publications.)
The bottom line for the publication is that its prestige rises with better quality writers and falls with those who don't have the talent or ability or discipline to turn out good copy. More on this later.