I wouldnt suggest going with the WiFi. Ethernet is the way to go if your serious at all about gaming.
Needs:
Headset (
Astro's, or Turtle Beach's - i myself have turtle beaches and i LOVE them, they are compatible with PC as well and come with a free 1 year warranty. They are great for movie's as well if your going to watch a lot of movies on your Xbox via Netflix, which a lot of people do. Turtle Beaches HERE - i have the X11's, flawless. Astro's HERE I myself don't have them, but many pro's use them over Turtle Beaches for some reason. )
Wireless controller ( They are rechargable with 2 options, plugging into the 360 for charge, or new batteries. I myself just use the battery packs that come with the controller and recharge with my console, fast, cheap, easy )
Some good starter games, you dont want to get bored quick. Try getting some popular games so you meet some good friends on xbox live while your getting better.
Depending on your TV, get an HDMI cable. They can switch between normal, and HDMI, depending on your needs.
Hope this helps