Building a computer doesn't take a "LOT" of knowledge, persay.
All you have to do is go to the system forum and make a new post using the template provided, and tens of people will jump out with good builds for your price/intended use. Once you have a list of parts you are going to use, read the assorted assembly guides on the forum for how to actually build the computer.
Once you've read them (they have pictures as well), order the parts if you are comfortable, and build away! We're always here on the forums to help out with new builds and troubleshooting as well