Reading widely helps with words. It helps somewhat with grammar. What it is needed for, really, is --
No, the warning comes first.
This is a proposed writing exercise. DO NOT SEND TO EDITORS! If you send to editors, I will pretend I never heard of you!
But, to develop your style, one thing that really helps is to write pastiches of writers you admire. It helps a lot if they are great stylists, but the real point is to master the art of making words jump through flaming hoops rather than sit around on the page. Trying to sound like any writer is aiming for precision in writing.
In some respects, this is not really advice, because many people just fall into it. Many (most?) young writers tend to fall in love with writers' styles and try to imitate them. It is not for nothing that Ursula K. LeGuin dubbed Lord Dunsany "First Terrible Fate that Awaiteth Unwary Beginners in Fantasy." It's hard to imagine how many writers have churned out how many reams of Lord Dunsany imitations -- eighth rate imitations of Lord Dunsany -- as no one can write better imitations of his "crystalline, singing prose" than eight rate.
On the other hand, even eighth rate Lord Dunsany imitations teach you a lot about how words fit together to produce style.
And once you get through fits of Lord Dunsay, J.R.R. Tolkien, Ursula K. LeGuin, and many other writers (good or bad stylists), you have learned lots of effects you can produce by putting together words in all sorts of grammatical structures.
Lots of writers is an important point. It's one thing if people can tell that a writer is an important influence on you. It's another to write only pastiches. (That warning up there is not kidding.) And for another matter -- writers are good at various things. Imitiating many different writers teaches you many different things to do with your box of tools.