I have one Interceptor, and bought four of each Wave 2 fighter plus two Firesprays and one Falcon.

There are squads I want to try with 3 and 4 A-wings, since their low cost and ability to mount missiles make them fairly effective alpha strikers. There are definitely squads I want to try with 4 or even 5 Interceptors. I don't have a good reason for buying the second Firespray, other than I wanted extra Stealth Devices, and had a gift certificate burning a hole in my pocket.

It's hard to say how many "enough" is, though. I bought the upper limit for the number of Interceptors you can field, and almost as many A-wings… but I'm interested in tournament play and having the flexibility to build (almost) whatever list occurs to me. I'm also the main supplier for a couple of friends who like the game but aren't able to invest in it the way I am, so I want to make sure I have enough for them to play what they want and/or what looks cool.

…I'm not sure I'm making much sense, but I hope that helps!