So, I've bought this game and did not regret it but it seems too easy.
This is the strategy I use on every map (so far completed the first 5 including the tutorial map):
1. put all ships on the upper corner as close to each other as possible
2. set the following tactics for all ships
- vulture: kill the seriously damaged ships first
- cooperative (not sure about the name): focus fire on those ships which are already attacked by others
This worked flawlessly with the first 4 maps with the turorial ships and I did not even used up all resources (only around 3/4 I guess). For the 5th map, I designed new ships since there is an anomaly there (no shields).
I have yet to try the maps on harder difficulties but I don't see the reason why the strategy above wouldn't work (seems the best). I think I'll just need to design some other ships with better equipment for the win.
I do have a question. On the map selection screen, I see only around 15 maps. Is that all, or I'm going to unlock new ones as I progress? It's not just about unlocking them since I cannot choose all right now, but if I already see all the available maps, then this game does not have a long playing time at all. I' bought all the DLC's as well, I don't know if it matters or not.
BTW: I don't understand the game's title. Gratuitous basically means free...
edit: corrected a lot of typos...

Second definition:
"being without apparent reason, cause, or justification"

It's using gratuitous to say that the battles are big and over-the-top in terms of explosions, number of ships, whatever.
The main strategy is really having the appropriate ship builds, rather than where you place your ships.
The harder difficulties are definitely harder, and bear in mind you've only played a handful of levels.
Very fun game.

I'm thinking about buying this game on Steam because there is nothing more awesome than the title of this game.

All I know about the game from previews I sounds like a lot of fun.
How is the MP mode? Such games probably make more fun with other humans on the other side...

I own the game and two of the expansions, but I personally have a like, hate relationship with it. While it can be fun to watch battles take place that is all you get to do; watch, no control what-so-ever.
I bought the game during Beta and it has had many tweaks and revisions to it (e.g. how close ships can now be in relation to one another during deployment). It seems to be well supported and the best thing I can say is that is completely DRM free.
The aspect I dislike is defining the rules for your ships, I find it tedious and rather boring. If you do not choose well, you lose the battle and have to re-tweak your ships once more to set them on their way again and sit back and watch the battle, over and over again.
There is no multiplayer in the game. What there is though is, the ability to create your own fleet and submit it online for others to play against. They can download your scenario and see if their fleet is better than what you devised.
Ultimately it can be a fun game for a limited time to develop ships, add weapons, shields, defenses, etc., and then set your creations free to battle. After awhile just sitting and watching the same thing take place over and over again, loses it charm.
As I say I have a like, hate relationship with this game, so I may not be the best to determine your decision making upon. Let me simply say, GSB is uninstalled much more than it is ever installed on my system.

Whoop whoop! GSB gets a campaign! At last! I like the game, but I honestly thought it wasn't worth the SGD35 I paid for, as Faithful as summarized for me. Hopefully the campaign will be free, but even if it's not, I'll still get it if the price is reasonable.

Good news indeed. I finished 90% of the maps in a few hours even on hard without a sweat. I hope for a free campaign otherwise I don't think I'm going to buy it.

So, how do I get this campaign in my Indie Bundle (forget which one) copy of GSB? I redeemed a key on Steam and have been using that copy to play, but there's no campaign option in it.

I do find the game fun, I'd like to have a friends list for the Challenges because it's much more fun to fuck with your friends than some random noob online (I'm probably a noob myself, I had to read a guide to figure out why my ships kept under-performing, now I get it, but damn, 90% of this game is in the ship builder).

Also, you can get all the unlocks very early, I was hoping for more variety, though at least in this game all the beginning unlocks still have their place even on the hardest maps and best ships, that is saying something.

It's a DLC called galactic conquest. Haven't tried it myself yet, but since I really loved GSB I'll get it as soon as I have disposable income, because it looks really, really good and adds some purpose to the battles.

But the point is beating them on expert with as few resources as possible. If you use max resources, yeah, it's not too hard. There are some maps where you can simply load a bunch of Cruisers up with Fast Firing Missiles and plant the minimum number of ships needed to not get obliterated. But you can also do even better by building specialized ships (e.g. front line with massive defenses, mid ships that can support front lines and dish out some damage, and the massive rear cannon ships, almost all power, enough defenses to not crumble under fighter swarm and that's it).

I bought this game, haven't tried it yet. Should I?

You definitely should. It doesn't take up too much time, yet it's really good fun.

Yeah, you could plow through "Normal" in a single evening, 2-3 hours. But it's once you start playing with orders and ship builds and understanding what everything does that all the complexity starts to show up.

If you ever get stuck on a level that's stupidly hard, mass Cruisers with Fast Firing Missiles or mass Fighters with a single Laser (the one you get at the beginning, the other one is too ass to penetrate armor, also, make them as fast you can, Armor will hurt you in this situation) will usually solve it for you. The fighters are awesome because if they fire inside the shield bubble of a Cruiser they get to bypass the shields entirely.

And finally, Torpedo Fighters, these should be good, they sure sound good... but they suck, seriously... Rocket Launchers are better.