Also, any videos that you have seen will not seem real after you step into VR.
The package you buy is great from the moment it is set up and the software and games installed. Adding a third sensor makes room scale tracking easier than with 2 and in my opinion worth the extra money (even if you play seated as I do most of the time - a swivel chair and headset makes for some 'interesting' occlusion issues!) if your budget allows it.
Be prepared for some real surprises if you do buy - word descriptions don't even get close to the amazement when you don the headset for the first time!