You should be able to find something for each of those chord changes within this simple scale;
1/3 1/2 1/open 2/3 2/1 2/open 3/2 3/open.
Otherwise know as G F# E D C B A G.
Without knowing the time signature or melody it's a little to suggest actual combinations. What do you "hear" in your head? Hum it out loud and hunt the notes down. More often than not they're right there in the chord shape your holding.
I rarely think about the notes in relation to the key I'm in, "Does this belong here?". I prefer to trust my ears, if it sounds like shit then it probably is!:~)
Keep at it, your moment of revalation is just around the corner!
C-flat.