Hacking Circuits Together Using Existing Schematics
There's nothing wrong with that basic approach. Chances are the PCBs that you are using were themselves adapted from typical application circuits for each of the parts. 

Speaking of which, I think it's better to look up (and read and understand) the datasheets for each the parts before you blindly transfer the schematics to your own board.  You'll have to find exact part numbers, pick packages and so on anyway. The components and the schematics may not include enough information even to just purchase new parts.