To make my cat happy, I’m going to adopt a second cat!
Hummm… are you sure?
Don’t do it. If you adopt a second cat it will be for your own pleasure. Cats are "territorial" beings, they have a hard time sharing their domain.
The main causes of visits to the vet for cats are dermatitis and cystitis. These diseases can be triggered by the stress of having to live with other cats.