I hear significant discussion about learning ballet dance at home without a teacher. Even by persons who aspire to professional ballet performance, starting at a late age. This is thinking in a bubble. Instructional ballet videos, and ballet theater performances are excellent learn-at-home guides, if your own ballet is done in a dance class.
You cannot learn ballet at home without a ballet teacher. Experience with gymnastics, Pilates, or martial arts, will not help you learn ballet by yourself. It WILL help you learn ballet, in a ballet class, and help avoid dance injuries.
Body awareness, physical strength, balance, flexibility, all contribute to learning ballet. But not without a ballet teacher. Don't get depressed about this, every problem has a solution.
If you love ballet, and if you love yourself, take ballet with a teacher. Don't waste time with instructional ballet videos or dance manuals if you don't have a ballet class.
Ballet teachers also buy teaching manuals to learn the finer details from. Does this mean anyone with no dance background can buy one and start ballet teaching? Of course not. Same for ballet training. You need someone to be watching your ballet positions, ballet movements, and ballet technique, and correct you.
If you have gained discipline and strength from some other training, that is wonderful. Look back on that former training and ask yourself, could you have learned all that by yourself at home from a DVD?
If your problem is lack of money for dance classes, ask your parents if you can find a way to change their budget, as in, what they spend on you. Would you be willing to wear cheaper clothes, or do you have to have the finest fashions? Would you be willing to get a job? Do some local babysitting? Even if you are under age to work, in most places your parents can get you a work permit. Is it astonishing that I would suggest this?
Would you be willing to learn to make pizzas for your family instead of ordering in? Or anything else like that? These ideas may sound silly to some, but if you're really serious about ballet classes and you show a mature approach ("I am willing to give in order to get") to your parents, they will probably respond more enthusiastically.
So, I have not given any instant solution here, but you will find one. Don't waste time feeling depressed if you think you cannot get into a ballet class and have to accept that you cannot learn ballet yourself at home. Just get a strong focused intention started toward getting what you want. Once you are in a class, progress faster with THE BALLET BIBLE which explains classical ballet technique, and will help you avoid dance injuries.