Are there differences in the amount of credits, experience and galactic readiness earned between bronze, silver, and gold difficulties?
I know this is only a partial answer but I'm looking for how much experience and creds you get from gold too so I thought I'd pass the info along.
Bronze: About 150,000 experience, 15,000 credits.
Silver: About 200,000 Experience, 30,000 credits.
As far as galactic readiness goes, I haven't really been watching but it's usually around plus 3% each time I think.
OmegaEffect answered Bronze and Silver.
Gold: ~250k Experience, ~75k credits.