How can I improve on my first attempt at graphic design?

the most important point to have trust in your ability try to follow and see a lot of professional designs search about it it will help you a lot and be updated with the latest version of programs cause there is new feature that you can use to facilitate your work 

It is of great importance to know at least basics of Art and hystory of design. In practise, do copy other professionals and figure out how they came up with their own solution / design. That should help you how to develop and improve your own work.

tools, first you should understand the tools of soft wares, give time to youtube, it will help you understanding multiple use of single tool,