When I go to a tournament or play against someone else who has there own stuff cards aren't too much of a problem, but I spend a lot of time convincing my friends to come over and play with my stuff. This shouldn't be a problem since I own EVERYTHING. I have three or four of most ships, and 8 TIEs. But I only have 1 YT-1300, 1 Firespray, 1 Shuttle, and 1 HWK. These just aren't ships that you need a lot of. And (with the exception of the HWK) they cost twice as much as the other ships. They are also where you get some of the best cards.
Here are just a few of the cards that I would like more of.
Advanced Sensors
Gunner
Stealth Device
Engine Upgrade
Heavy Laser Cannon
Anti-Pursuit Laser
Maybe Recon Spec (I haven't tried him on the Firespray, but he is supposed to be awesome.)
I plan on getting another Firespray and another Shuttle. I think I will play with more than one of these, but I don't think I would play with three of any of the big ships more than once (each) to try them out.
However, someday I really want to run 3 ORS all with Anti-Pursuit Lasers.