What computer should I buy? (expert help please)!!

I don't really think that you need more than $500.

A month or two back I was trying to do the same not for gaming but for design mostly. I found that you can get a computer with socket 775 motherboard (which is easier to upgrade the processors since it's an old socket), buy an i3 processor (which is already interesting) and good memory and ssd drive and such. Later you can upgrade things.

The beauty of a desktop computer!

Today I wouldn't buy a Macbook with i7. I would go with i5 and make a hackintosh.

A thousand is a lot of money and it really depends on what you're trying to achieve but... You can make a good computer under that.