Attaching a video description in your gig is helpful for increasing your sales and by that way it is a great chance of appearing your gig in the first page of the search result.
Try to use key content in your video that you are offering for sales. It may helpful if you can use audio in your video. And try to make it professionally.
And one thing is most important I think , if you can show yourself in your video. So that most of the buyer can relief from the misunderstanding.
It is for the new seller . I think it is the best way to share my experience with you. Hope it will help you.