So each time they release an “expansion” they do it as a set of packs. So it feels like less than that…
There are three core sets, Original, Colony Wars and the new one is Frontiers (It isn’t out yet, but should be shipping from Kickstarter soon). I would highly recommend each of those.
Then some of the expansion packs add ships and bases, and others add new types of cards/mechanics. I would focus on the ships/bases ones first, then add the new mechanics.
The ship/base expansions are as follows:
- Crisis - Bases and Battleships
- Crisis - Fleets and Fortresses
- United - Assault
- United - Command
The Crisis expansion also has “Heroes” and "Events"
The United expansion also has “Missions” and “Heroes”
Missions, Heroes and Events are all new mechanic-type cards that add to the game. Of these, events are the more swingy, and can result in things like being able to buy an 8-cost card in the first turn. It gets crazy.
Gambits and Cosmic Gambits are another new mechanic. Each player starts with 2 gambits in play and they provide an ok, but consistent effect throughout the game, or they can provide a one-time, but pretty good effect.
There are also some promos. You can probably get the year-one promos on ebay pretty easily. I ordered the year two promos with the Frontiers Kickstarter.
Anyway… I would start with the core sets, then pick up a pack here and there for the expansions.
For me… I’m all-in. I’ve purchased just about everything card-wise, and even doubled down and have gotten every single available game and expansion on iOs as well (though it is cross-platform and one purchase covers all devices).