Need help with a very tight budget build

Hi I am fairly new to this community i do some looking around at builds for gaming pcs and i have to be honest, to me its all a little confusing. While i have a basic knowledge of computers and parts for the most part, as far as processors and in depth components i am pretty lost

My main issue with getting a gaming pc is money, i am currently very tight as far as my budget goes

I am however able to use a credit card (my preferred payment option)
so i figure i have 2 options here
on a $1000 budget (trying to keep my options open as far as performance)

1 : I can build one myself and hopefully the website will accept a credit card as a payment

2: Settle for a Dell.com/ Alienware "gaming" computer (I have a dell credit card)


My main concern is that while I don't need my pc to be over the top in performance (shouldn't be over clocking or running high end games like BF3 or Skyrim)

I plan to play games such as Diablo 3, TF 2, Torchlight 2

I do however want to keep my pc open for upgrades I want it to be able to be flexible, nicely cooled, and easily cleanable, on top of keeping my game play smooth and unhindered

I hope I am not doing this wrong or in the wrong spot, I really could use some pointers as far as a nice performance build for around $1000

or if maybe what I am reading about dell and alienware isn't all bad and it could be something i could settle for