If the FC lights up with the USB then it is likely not getting the 5v/Gnd from the PDB, do not get too far ahead of yourself, lets look at this logically with knowledge...
First plug up the battery (NO PROPS!) and see if you get the 2 Red LEDS on the bottom board. If you do then the PDB is fine and it must be a wiring issue.
Also, it will not be fully ready to fly yet, there is more to configure in Betaflight. I can't remember what this was, is it a PNP, BNF, or RTF?
If it is a RTF then I am a little light on the TX setup and Betaflight config as I use Frsky Taranis so it is a bit different, but I know there is a few videos just for the RTF version out there that if followed should help you configure your arming switch(s) and Failsafe and test it all out. Let me know and I will dig up a few videos for you.