Also.. if you haven't considered it... boxes.
If you don't have any normally hanging around the house, get some of the smaller packing boxes that kitty will fit in, cut holes in them, and stack them and duct-tape them firmly together. My cats always loved box towers to run through, hide, and chew/claw on. You can semi-wrap them in wrapping paper to make them more pleasing to look at.
They're also cheap to make and replace (if yours is anything like mine, you'll be replacing every two to three months), and you can do variations on the patterns to give a different experience.
If you don't have any normally hanging around the house, get some of the smaller packing boxes that kitty will fit in, cut holes in them, and stack them and duct-tape them firmly together. My cats always loved box towers to run through, hide, and chew/claw on. You can semi-wrap them in wrapping paper to make them more pleasing to look at.
They're also cheap to make and replace (if yours is anything like mine, you'll be replacing every two to three months), and you can do variations on the patterns to give a different experience.