Yes, I think you should have two sets of everything.
I successfully introduced a second cat into the household. There are lots and lots of threads here explaining how to do it. I spent a long time (at least six months) looking at the cats for adoption, and finally when I was ready to spend the time with the kitty introductions, I found one with a personality that I thought would suit Sam. (And ner name is Bailey). He was about 6 1/2 and she was about 3 - according to my vets best guess. I thought that I would look for a cat that was smaller than Sam, which is not hard to find, as he is a big guy, and I wanted to get a female, thinking that would be less threatening than another male. I have no idea if that really made any difference, I am convinced now that the personality traits of cats vary so much, the size and sex don't really matter as much as the individual cat's temperament.
I already knew that Sam liked other cats, I had taken him to my sister's house, and saw that he interacted well with her cat. So I think that you need to see the new family member through your cat's eyes, so to speak. If you have a very calm and laid back cat, you need one that isn't too wild. If you have an energetic cat, you need one that will like to play. I somehow knew when I found the right cat to fit into our household. And they got along really well right from the beginning.
However, I did make sure that I fed them out of separate bowls, and gave them separate spots to sleep, just to avoid any jealousy problems. And two cats need at least two litter boxes, and probably 3 if you have room.