Many virtual assistants love the freedom of their jobs, but feel like they are not particularly flexible when it comes to advancement. To some degree, this is true. After all, you may not have a lot of upward mobility within a company if you never meet the owner in person or even correspond directly with a supervisor, as is often the case with VAs who handle help desks and customer service. However, just because you are not going to move upward within a company does not mean that you cannot enhance and improve your resume and job skills while getting paid to do so.
Talk to your employer - or your direct supervisor - to see if there are responsibilities that you can assume that might make your job easier and expand your skill set. There may be software available that could smooth many administrative processes for you and make your work more easily accessible to your employer as well. Learning to use such software can make you more marketable even as it saves you time and effort in your current position. Usually you will not need to invest in the software yourself, either, which will save you additional money.
When you are working with clients, determine which of their problems or issues you believe that you could resolve on your own, if you had the authority to do so. This is a good way to expand your skills and experience as well while making your work life easier. After all, if you can close more cases or help tickets without assistance, then you will not have to field return calls from people who fear that they will not be helped or who think that they have been forgotten.
Finally, keep track of everything that you do. While this may not directly expand your knowledge and ability to use office tools or software, it will help you keep a close eye on your abilities as they stand currently. In many cases, you will see that you are selling yourself short on your resume by neglecting to list responsibilities that you fulfill every day in the course of your work.