well for nice gameplay and "GAMING" on a laptop you will spend more than you expect. Gaming Laptops are more than a gaming desktop would be. It also depends on which games in general are you wanting to play as Crysis, GTA4, Stalker Clear Sky and some others are very CPU or GPU dependent meaning you need a very high end machine to play it.
I have helped you in other threads and this route is not the way to go for gaming unless you want to spend minimum $1000 and that will still have a slow video card in my opinion. To get a nice gaming laptop $1400-$2000+.
For $1000 you could get one like this:
http://www.cyberpowe...-7800_Notebook/I would not go any lower performance or cheaper than that as the nvidia 9600m-gt would be my starting point for a gaming laptop.
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If you go the desktop route get some kind of dual core core 2 duo (intel) or quad (intel or amd). IMO I would not go for the AMD X2 cpu's as they are getting pretty old now..
4 GB ram of ddr2 can be bought for $45 or less now. On the video card this is the most important part, get the fastest video card you can afford as this will be your #1. On the cpu you do not need to get an expensive one just look for a dual core with a higher clock rate or any quad will work.
I would save up until you have minimum $800 to spend but $1000-$1200 will get you more of a system and $1200-$1600 even better.