Convince for a cat?

I want a kitten so bad! But my mom won’t let me, she say we can’t afford it, but belive me we can, she doesnt want a cat, and cause she thinks we have to much pets, we dont, we only have three, a hamster a dog and a chinchilla,and she doesn’t even help take care of them, I do all the work! All she does is bring my dog to the vet. I promised her I would keep to litter box and food and water in my room. And I would feed it and clean its litter box, I also have about 130 bucks I want to help her buy some stuff. I even wrote 2 reports and a book on kittens. I’ve never had one before, and I just want one I told her she will grow to love it, and get it declawd, but probally not get it declawed, just keep it’s nails short, cause she thinks it will scratch on the furniture, when it does I will stop it right away, and if it does it non stop for about 2 months we will see about getting it declawed, I know its painful for them but are furniture is brand new and it cost about 3,000 dollars.at the pound I want to adopt form kittens are only 90 , with the other money I can help buy some food and toys.At school nobody is home, so I would just put him/her in a cage or make sure my room is absoulty spotless with nothing out and just leave it out with my door shut. Please give advice, I know a kitten is right for me because I want a animal to share my feelings and emotions with, and that I can hold ( my dog is to big, hamster small, chinchilla to wild) Please help!