Recently, I've been able to spec out a low budget (<$800) server that fits my needs, however you need to be more specific as to the server's role. Windows network? Unix/Linux? Mac? Storage/RAID? Application Server? For example, if this is a file server where either files and/or databases would be stored, then RAID becomes a much bigger issue so a RAID card, and possibly backplane may add on to your cost. If this is a simple email or web server, RAID may not be a priority thus, reducing your cost.
I wouldn't recommend Dell or any other vendor in terms of low-cost unless expandability options are a priority. If you needed the ability to scale up, then a vendor may fit your needs better, but it sounds like money is your only concern. I can help you, and I'm sure others would be just as willing to help, but specs as "cheap" isn't really painting a picture. Until you specify some intentions, it's difficult to help you
attain that low budget server you're looking for.