I'm glad you both have caught the gaming bug with this: welcome aboard, both of you!
As listed above, Hrathen has an excellent outline of the individual ships. I'll say that if you're sticking to a budget but want to have a lot of different stuff, just pick up one of everything (excluding the almost mandatory second core set). I don't play Imperials often, SDCC, but I will say that the Firespray, Shuttle and Interceptors are all a lot of fun to play, since they are point heavy, but often well worth their value on the field.