I know a few people who are starting to get into X-Wing or have expressed some interest in it. So I figured I'd post about that instead of how December is the month 40K died.
The thing to know about X-Wing is that ship upgrades are distributed among the different sets. So, I'd recommend collecting both Rebels and Imperials if you want to get tournament level serious with the game. Fortunately, the game has fairly good balance right now, so for casual play you can do well with just about whatever. I would say the game is more about movement than list construction, and at the national tournaments people continue to do well with basic wave one ships and upgrades.
Still, if you're just getting into the game, you are probably wondering where to start. I'm going to run down all the expansions and give my opinion on what you need them for from the perspective of both Rebel and Imperial players.
Starter Box: Required for both Rebels and Imperials.
You can't skip this one. You get the asteroids and movement templates and a few other required game play materials. For the rebels you get Luke, Biggs, and R2-D2. Still very strong cards in the meta. The Imperials get some named TIE pilots. TIEs are the bread and butter of most Imperial lists; cheap and effective.
X-Wing: Rebel-Buy 1-3; Imperial-Don't Buy
The basic X-wing is a strong ship with a good mix of attack, defense, and utility. The stand-alone pack gives you different pilots than the ones that comes from with the starter. Namely, Wedge; arguably the best pilot in the game(Pilot skill 9 and targets roll one less defense die).
TIE Fighter: Imperial-Buy at least 4(including the starter box TIEs); Rebel-Don't Buy
Like the X-Wing, this one comes with different pilots than the starter. Also like the X-Wing it comes with one indispensable pilot. In this case, it's Howlrunner. She gives nearby Imperial ships a re-roll on an attack die. After movement, the next most important thing in the game is action economy. Granting re-rolls without having to spend an action to do it is an extremely powerful ability in this game.
Y-Wing: Rebel-Buy 0-2; Imperial-Don't Buy
The Y-Wing isn't a bad ship, but none of them can take an Elite Pilot Talent. This means they haven't benefited from newer releases as much as some other ships. Dutch gives out free focus locks; a very powerful ability. They can also take turret weapons, and the ion cannon turret is very effective. Another strike against them is the lackluster utility of Photo Torpedoes. They require too many actions to effectively use and cost 4 points each to boot. Rebels don't have the points to spend on such inefficient options.
TIE Advanced: Imperial-Buy 0-1; Rebel-Buy 0-1
It's essentially a TIE with shields and the option to take missiles. All of the pilot choices are just too expensive except for Vader, who is my second choice for best pilot in the game. It also comes with Swarm Tactics,and Squad Leader Elite Pilot Talents. These are universally good action efficiency cards, and a reason for even Rebel players to consider picking one up.
A-Wing: Rebel Buy 1+; Imperial-Buy 1+
Maneuverable, but with weak offence and defense. It's not the greatest ship in the game, but it can use missiles and has the only non-unique rebel pilot card that can take a Elite Pilot Talent. Tycho is also another of the game's top pilots. The A-wing comes with and Elite Pilot Talent called "Pushing the Limits" that gives you an extra action for the cost of a stress. It's an essential card for an elite pilot based list. Plus that song from Scarface goes off in my head every time I use the ability in the game...so, bonus.
TIE Interceptor: Imperial-Buy 1-2; Rebel-Buy 0-1
An up-gunned and more maneuverable TIE with two really good pilot cards(Tur and Fel), but they are a little too expensive to use more than one or two. It comes with an EPT that improves the boost ability to include Hard-1s. It could be useful for some crazy Rebel lists.
Millennium Falcon: Rebel-Buy 1; Imperial-Buy 1
It's 360 degree primary weapon make it one of the better Medium sized ships. The generics aren't any good, so you need to take the named pilots who are a little too expensive to use more than one in a list. This is also the only place to get the Shield and Engine Modification cards, so even Imperials need it.
Slave-I: Imperial-Buy 1-3 Rebel-Buy 1
It's an X-wing with more shields and hull. It's got a forward and backward firing arc, but it's hard to maneuver. The generics are really good, so you can build an effective 100 pt list that uses 3 of them. Rebels need it for the Gunner crew card, and the Stealth Device upgrade card. If you also play B-Wings, you'll want to poach its heavy blaster cannon.
B-Wing: Rebel-Buy 0-2; Imperial-Buy 0-1
A aery expensive ship with a lot of hull and shields for its size. They do torpedoes better than Y-wings, and are very customizable with access to BFGs, Systems, and EPTs. Imperials may want the unique system and BFG card for their big ships.
TIE Bomber: Imperial-Buy 0-2; Rebel-Don't buy
A TIE that makes up for 1 less defense die with 3 extra hull. They do expendable ordnance really well, and the named characters are good. Nothing here for the rebels though.
HWK-290: Rebel-Buy 1, Imperial-Buy 0-1
Stat wise the ship is very forgettable, but it is almost an indispensable support ship for Rebel lists. It's also very modifiable, can equip a 360 degree turret, and is the only small ship that can take crew. Imperials could make good use of the Recon Specialist on their big ships.
Lambda Shuttle: Imperial-Buy 1-2; Rebels-Buy 0-1
The imperial's support ship. Good stats and base cost, but pitiful maneuver dial. Can be configured with upgrades to be really annoying. Rebels want its upgrades to do equally annoying things.
From the spoilers seen so far the Imperial Aces pack is going to be a must buy for both factions as well.