I am not an eBay user but my parents have been cleaning their house and have been giving me my Barbie collection. It is not something I still collect and I don’t really have room for them so I’ve been debating trying to sell them on eBay.
If your Barbie collection is in good shape, stop debating and start selling. I sold my Barbie collection on eBay 20+ years ago and did quite well, but to be clear, I had a lot of original Barbie outfits in excellent condition. The rarer they are, the more $ you can get for them.
I had a great experience with most buyers. I had only one disappointing sale where the buyer claimed never to have received the outfit, so I had to refund their money even though the package was tracked and had supposedly been delivered. But things do happen. And, as a seller, if you want to maintain an excellent rating on eBay, you have to adopt an attitude that the buyer is always right.
Also, before I started selling, I purchased a book that delineated the details of all the outfits, so I knew if what I had was complete, and it also helped with describing everything. When I finished selling, I sold the book too!
Good luck! And let us know how it goes.
ETA: I just saw that you have some of the outfits that're still in their boxes. That's extra $, assuming the outfits themselves are in good shape. Collectors love having things that include the original box.