Okay bud first of all laptops shouldnt be used for gaming .. well thats what i believe.
you should build a pc its not that hard and you get the best preformance for cheap
now lets start with the basics you will need a case. now this is important beacuse you do not want a small case nor a big one for no reason so lets find some hmm..
CASES
You dont need to worry about how the case looks as long as its good i guess
mid towers are fine but it can sometimes get cramped
mini towers maybe way to small to fit the good ****
and full towers are down right expensive and not that much needed unless youre building a beast as gaming pc with freaking 5d
so mid tower
http://www.amazon.com/Cooler-Master-...computer+cases
seems nice. you can fine anything that suits you.
PSU
now a psu(power supply ) i suggest a 500w psu since thats the need for most graphic cards. psu is where you do not want to go cheap on.i had a 160wat psu and a nvidia 8400gs and the minimum requirements was a 300w and i ended up frying my graphics card ;(.. most trusted brands are antec,crosair,xfx,coolmaster,seasonic
a 500w is typically about 50-60
http://www.amazon.com/Corsair-Builde...s=power+supply
motherboard
the mother board is crucial this determines what processor you can put the ram etc..
http://www.amazon.com/LGA1155-CrossF...ds=motherboard this is an expensive one but good maybe for dual graphics card but i would choose something like this
http://www.amazon.com/GIGABYTE-GA-97...ds=motherboard which is all you need.
cpu
now you can get intel or amd. nvidia cards run well on intel processors and radeon runs better on amd. i suggest amd well cause i have that. modern games look for dual core at at least 3.0GHz
remeber the motherboard up top has a am3+ socket so the cpu has to be am3+
http://www.amazon.com/AMD-4-Core-Pro...ords=processor BOOM!
graphics card
okay now that that's out the way.. you will need a graphics card.
any graphics card works on a mother board as long as its in the right place pci express of course. if the card says 2.1, 2.0.,3.0 pci express it can still work in a 1.0 x 16 slot but not on it maximum performance. now graphic cards can vary it depends. for high quality settings for all modern games i suggest the radeon 6770
http://www.amazon.com/XFX-Radeon-677...&keywords=6770
memory.
make sure your motherboard can handle it.
buy two of these
http://www.amazon.com/Crucial-CT2566...ds=ddr3+memory
im not sure if the can work on that gigabtye motherboard but do some research
Harddrive
now 1tb is good but you can go lower if you want
http://www.amazon.com/WD-Blue-Deskto...rds=hard+drive
cd drive
something basic
http://www.amazon.com/Asus-24xDVD-RW...s=cd+rom+drive
others
the cords you need dvi,vga,or hdmi what ever you want or need. theres not much more you can get except tools i guess and that will be about 20-30
so lets calculate.
case-50$
motherboard-100 $max
psu-60$
processor-100$
ram chips depends on the size 30-40$max
graphics card-120$
harddrive-40$
cd rom-20$
accessories-10$
total- 510
with those items i think they will be cheaper

i just kinda rounded them a bit more.