Through being or by being

 I hope to improve my skills bybeing a member of ...(an organization )

This is a tricky choice between prepositions, and you will find compelling arguments for each choice.

So as not to reinvent the wheel, I suggest you carefully review this learned discussion on the topic (http://english.stackexchange.com/questions/25459/what-general-rules-govern-the-usage-of-by-versus-through) and make your own best judgment.

Shawn