Hi Sarah,
First, congratulations on deciding to start your own VA business. The first thing you can do is write down ALL of the skills you are good at. Then, go through the same exact list and cross out the things you do not like doing (let's face it, there are some things we are good at, but we just do not like doing them.).
Once you have that list narrowed down, look it over again and see if there are any similarities between the skills that are left. Can they be combined to make one (or two) nice niche for yourself?
Also, you said you have extensive knowledge of event planning. Is your list of skills sought after by event planners (a possible target market perhaps?). Even if they are not currently, can you think of a way you can market them to event planners so they realize they do NEED these services from a VA like yourself?
Finally, create a second list. This list is of skills you don't have or aren't that good at, but you enjoy (or think you would enjoy). Keep this list and slowly start to learn one new skill at a time. My philosophy is that you should never stop learning.
I would love to know what you come up with! Good luck!