You really only need to own all the stuff for tournaments and maybe games against players you don't regularly play against. Buy enough to physically play any lists you've thought of, tried, proxies, etc etc etc that you'd want to take to a tournament. You'll be more apt to play the list more if you physically have the ships, which lol make you better at it.
I personally get at least one of every ship, then buy more once my list building needs require.
