It really depends, successfull Dj....well gotta define succesfull first, playing out every weekend? I'm not sure thats wht you mean, but to me thats successfull, but then I'm a music whore, all I want to do is write and play music, dont really care if I can only just afford to live it up, long as I'm playing and writing, I'm lucky enough to play out allot, but definitly not successful in terms of £ and releases. maybe one day
I think to make it to the top as a Dj, you have to have something special, either a unique mixing style that sets the dancefloor on fire, or music which is fresh enough to do the job for you, or your own music, long as its good