You will need to purchase the Wii gaming system, and the Wii Fit game. The Wii gaming system comes with the Wii sports game included, and I am satisfied with the tennis game on Wii sports. Another tennis game that has gotten great reviews is Mario Power Tennis.
The Wii gaming system and the Wii fit game come with all the cords and controllers that you would need to begin, but if you want to play your games against another person you will need to purchase another Wii controller. I would also suggest either getting a charge station for your controllers, or purchasing plenty of AA batteries. If you want to see a charge station for the Wii controllers you could look here:
http://www.bestbuy.com/site/olspage.... I hope this helps!