I am a relatively new Armada player having only done a handful of games. I am the sole owner of the collection among my friends, same for x-wing.

I know with X-wing, if I pack about three large and medium bases and eight small ones, I have enough for either party play almost whatever we want that isn’t weird jank.

The Armada bases are giant. What is the average amount of each size I should carr?

I think at most you can get 3 large ships, or 7 medium ships, or 11 small ships. Doubled for 2 fleets. But nobody sane will have that many medium or small ships. So probably a total of 6 large bases, 6-8 medium, and 12-16 small bases. 4/6/10 might be ok for most games. I'm sure someone with more experience can give better numbers.

This is assuming 2 400 point fleets.

3 Larges, 4 Medium Bases, 10 smalls should be good.

Here is another option. When I show up to game at my FLGS, I always bring two complete fleets (one Empire and one Rebel) and give a friend or new player the choice of what fleet to play. Unless your friend gives you their list beforehand so you can pack the stuff for their list, this option keeps you from carrying around (sometimes a lot of) excess game pieces. This has worked really well for casual gaming and for getting new players into the game.