Well there are two different questions going on here. The OP stated he wanted to build his own arduino board and a second topic of quality/usefulness of inexpensive Asian nano/micro/uno boards.
My thoughts are unless one really just wants the experience/educational value of building an arduino from components, it's just not a cost or time effective effort. Better to put the time and effort into a shield or wired board that does something useful or interesting. Even for just bread-boarding it's hard to beat a < $10 Nano board that just plugs into a breadboad and has the usb connector ready to go and can even have it's bootloader updated to the latest optiboot version. And for insertion into a PCB it's hard to beat the $3 pro-minis. I've bought a few of both and seen no problem in quality or performance.
However that doesn't change my recommendation that a beginner should start off buying one 'real' arduino Uno board, just call it the 'entry cost' to our great community. 