Graves,
I think a good solid buy for Imps is core, vsd, gsd, and the fighters. You will have the 3 caps and enough fighters to make a tournament list and be able to tweak it slightly in numbers of upgrades and fighters. If you don't all that I think your going to find it difficult to tweak your tournament list. The 3 caps ships and and the core fighters will leave to close enough to get to a tourney list but I think it will be very limited. If you dropped anything I'd drop the gsd because 5 fighters is probably going to be too few for a decent list and if you dropped the vsd I think you would have to too few points in the base cap ships.
As for a Rebel list I think core, neb'b, 1 corvette, and fighters. I'm just not a huge fan of the AFII model although I'll likely get one eventually. I think 2 neb, 2 corvettes will give a lot of options in whether to take a 2nd corvette or just more fighters. I doubt I will run a list with just 1 neb.
So my preorder is looking like:
1 core
1 vsd
1 gsd
1 imp fighter
1 neb
1 corvette
1 reb fighter
My wishlist for later:
1 ISD
1 AFII or perhaps a different reb when wave 2 is announced
My to make/mod list:
A modest number of freighters and transports so I can have scenarios with convoys etc. I'm thinking I'll use a few rebel transports from the star wars battles and add in a few misc spaceships from some other games.