What are you going to use for video editing? Video editing can be one of the most taxing things you can do on a computer. If you're just going to use something like Movie Maker, no worries, an i5 or i7 will be more than adequate. If you're going to use Premiere, After Effects or Avid... Well, you're going to spend a good amount of time waiting for renders. Gaming actually is less stressful than some Premiere + After Effects projects 
You want to work with as many threads as possible. The more cores you have the less time it will take to render scenes. Especially f you use mixed content (like mixing different video source types). The more RAM you have the more material can be used simultaneously without having to swap back to the hard drive. Your video card should not share memory with the system. If you're going to work with 3D (After Effects & Premier use 3D elements), then you'll need at least a moderate class video card from nVidia or ATI. The hard drive should be quick and as big as you can afford.
Video editing is a desktop's job really. Laptops should only be used to fill in the gaps or work on small projects. Even my i7 MBP with 8GB of RAM and nVidia 330M really struggles sometimes to push out video. At home I network my daughters iMac and at work my Mac Pro via QMaster so I don't have to wait 2 hours to render fifteen minutes of 1080p video.
If that's all you can afford right now, you could reduce the stress on your laptop by converting any video, stills and 3D to 720p or lower. Just doing that will cut render times in half. Just remember, get the best CPU you can afford, then video. The hard drive and RAM can be upgraded later when you have more money. With laptops, upgrading the CPU and video will be far more difficult, if not impossible.
Hope that helps.