Hey naked,
I thought I would share my experience with you. I started with two core sets and had never player armada. Then I bought a crap tone of ships with little to know though on what and where I was going. In retrospect I think the key is to hook up with local players that have a wide variety of ships for you to try out. Play several times to figure out your play style, if you haven't already from your previous fleet game experience. Getting to know the game through proxy cards and using the experience and expense of other players will go a long way for you to make your dollars, or pounds, go a long way.
For me I am a bull in a china shop so buying multiples of the ISDs and MC80s was the way for me to start, this was expensive. Then again, I am not playing for the competition I am playing for the fun of playing. In fact I lose more often than I win, but I have a blast every time. The game itself from a marketing aspect is just like X wing In The fact that cards are sometimes specific to particular expansions and your fleet grows as you make purchases for the cards you need.
Just my two cents. Have a great time and welcome to the community. May the dark side flow through you, crush your enemies and hear the Lamentations of their woman.