We recommend using your fire poker to push all ashes from the firebox down into the ash tray and then disposing of the ashes after every couple of uses. You'll want to ensure there is minimal ash material buildup in the firebox and ash tray so that your stove gets proper airflow.
Also, some rust is natural/expected and happens because your stove comes into contact with water. It is not harmful. If you want to remove the rust, you can clean your stove from time to time using white vinegar and a scrubbing brush, or several other inexpensive methods. Here's a helpful video with more options for removing rust from metal objects: https://www.youtube.com/watch?v=knAv9q0gIQM