Apart from speaking, writing is the most important skill you can acquire in life.
Clear writing is essential in all of the professions as well as in the academy.
Any improvement you can make in your writing, therefore, will be a great benefit. Style is also important and on that subject one cannot do better than to study The Elements of Style by Strunk and White. It is brief, powerful, and available from any decent bookstore for a cost that represents but a small fraction of its value. Buy it and read it. The Elements A paper is most simply an argument for a thesis.