Just to get a decent spread of cards so that I can leave 2 or 3 'ready to play' decks which Cycle would be the best to get?

I assume that the Core is the 'Basic' rules and each Cycle/Premium Expansion add new mechanics/keywords..

I was even thinking of one of the Premuim Expansions instead, in case I have to shop around for or wait for all the packs of a Cycle to be reprinted or arrive in the post

EDIT: on FFG webstore all products available.. thinking of The Imperial Cycle after reading the bumf on website.