Help me build a freenas


I want to build a freenas mainly because I am sick of copying code files from one computer to the other. my goal is low power consumption and relatively high speed. I got a cisco dpc3825 gateway/router. I never played with any network options on it so let me know if there is an advantage of upgrading a better router. My budget is $400. Storage capacity doesn't have to be huge as long as there is room for expandability, maybe 1TB for a start. 

Please help and suggest :) 

It's a little bit more than $400, but you could probably skimp in a few areas. I chose 5-star parts (probably why the slightly higher price) because with a NAS reliability is key. Note that with only one drive you won't have an option to use RAID for security against data loss.