Xbox help?

i want to get an xbox, but i'm a noob and have no idea what kind or how many gigabytes... help?

I got an Xbox 360 Arcade second hand with a wireless controller, a 20Gb HDD and a headset for €180, it's never RRoD'd or given me any problems. Rather than buying a brand new one (unless you have a big budget) try and find a used one.
Otherwise if you don't mind spending a lot of money get the newest version with 250Gb, i think there is a preorder deal going where you can buy it with Reach and a special Halo themed case.