im being asked to improv a couple of folk, blues, and rock songs soon and im not sure i know the right scales to use.

heres one
G7 C7 D7 C#7 B7 A7 B#9 E9

and any scales you would recommend for this song and upbeat folk style songs?
A good default is to use the pentatonic major or minor in that key. That's just a good way to start coming up with ideas. If you want a more jazz sound you could try the Dorian mode.