Ballet's appeal to Goths, I believe, lies in this fantastic, dream like quality.
Google 'Goth Ballet' and you will find dozens of pictures similar to this...
Ballet can incorperated into fashion easilly. I feel this is similar to Lolita fashion styles, with more flow and something of a simplication. Ribbons and stocking are items that are often found in wardrobes, and are perfect. Tutus, flowing skirts that go to the knee and shorter hoop skirts are also perfect. Singlets, corsets (to the looney in the back, of course you cannot dance ballet in a corset. It's just for show), plain t shirts and flowing loose shirts are good for top clothing. Colour wise, ballet often features pastel and pale neutral colours such as ivory. While these can be very effective as Gothic attire, perhaps you would feel more comfortable in black, grey, charcoal or even neon colours. Hair can be arranged in a bun, neat or deconstructed, or in an elaborate up do and secured with nets, ribbons or pins. In a performance, hair will always be off the face, but really you can have your hair however you like.
The 'Gothic' nature is really brought out through contrast. For example, stocking can be ripped and distressed, clothes can be stained, torn and embellished, huge chunky boots can be paired with pastel stockings and neat hair... The combinations are endless and any amount of DIY creativity can bring a ballet costume, or ballet inspired garb to be spooky, cute, mysterious, dark or even sexy, depending on your personality.
(Sorry for any ballet loving Cybergoths reading this. I'm not all that experienced with Cyber fashion, but I'm positive it can work. Oh, and if someone ever composed a ballet featuring vampires and droids I really would love them for ever.)
I don't encourage everyone to suddenly stop what they're doing and take ballet lessons and I'm certainly not supporting the idea that you must be rail thin in order to enjoy this look. That would be foolish and very unrealistic. Instead I think that the grace, elegance and attention to detail can be incorperated into our everyday dress, manner and lifestyle.