From what I know, eggs for donation should be of highest quality, and, in some cases, should be PGS NGS tested to avoid neuplodies. Eggs, donor or own, cannot be improved, at least at this moment. After egg collection, only best ones are implanted. Otherwise, a woman might experience a pregnancy loss or a future baby might have issues. In case a woman cannot find a donor, there are different solutions clinics usually recommend, such as egg sharing (https://fertilityroad.com/mag/egg-sharing-a-win-win-approach/),
egg freezing, embryo donation, adoption, etc.