If you can't house train a kitten to use the litter box, then I highly suggest you don't own any pet. You are not ready to take on the responsibility of pet ownership. If you must have a pet, try some goldfish.
What Should My New Pet Be?
Maybe something the 3 month cousin will enjoy and what you will enjoy. Maybe a turtle, bird, hamster. That's what I will suggest.
A kitten can be house trained and not use the box... When they have worms they tend to not use it, and when being treated for worms. Also if you do not have litter-boxes every 30ish feet of space that they play in when they are under 6 months they have a hard time. But I can understand the ruining stuff happens sometimes, and is not acceptable! I agree! Yes you should get a new pet, and I think a Hamster, or something would be good for you to start over again with for now.
Also as someone said, goats are GREAT pets! They don't require a TON of care, but can be pretty, and nice, and just GREAT pets! You can train them a lot of the same things you can train a dog (But dogs CAN still learn more than goats CAN learn, I don't care what ANYONE says), and they don't make messes. If you have proper fencing for where you are keeping them then they will not eat any of your stuff either!
Also as someone said, goats are GREAT pets! They don't require a TON of care, but can be pretty, and nice, and just GREAT pets! You can train them a lot of the same things you can train a dog (But dogs CAN still learn more than goats CAN learn, I don't care what ANYONE says), and they don't make messes. If you have proper fencing for where you are keeping them then they will not eat any of your stuff either!
You should get a new gerbil. I have 3 gerbils. Their names are, Jennifer, P.J and Pumpkin. Jennifer is the mother gerbil. She had 3 litters of gerbils. Its a long story. But to cut it short, I had a gerbil named Licorice, and a gerbil named Jennifer. They were supposed to be both girls. They had 3 litters of babies, we had to give Licorice away, and now I have Jennifer, P.J, and Pumpkin. I will always love and miss Licorice. And I hope he will too.
You Should get something like A Hamster or guinia pig, the only problem with those are that you have to clean the cage all the time. So something that might also be nice would be a little goat but if you get a goat you would have to have a decent sized yard.