I'm doing a wierd Vasari resource rush.
I think Ice / Molten colonisation are my first techs almost every time (depending on local map conditions).
What I'm doing is taking advantage of the AI's slow start, and (so far) other players' similarly tentative play. Also the poor militia defences of Ice and Molten worlds. I focus like crazy on economy: straight to civ tech 2 for colonies, grab all "easy" colonies nearby - that is, I fill my default fleet with the colonising capship and, what? 6 Frigates? But I do NOT upgrade fleet supply yet, so I can't comfortably take most Terran and Arid planets due to strong defence. Anyway, stomp some Molten / Ice worlds and some Roids, and then strap crystal / metal mines to EVERYTHING. Get Civilian infrastructure up to level 2 asap to prevent credit drain.
Vasari scouts can take extractors, and the AI doesn't seem to know how, while most players seem too lazy in the early game. This gives a surprisingly large bonus to income.
Sell heaps of stuff on the black market. Any AI in the game usually runs the Crystal price up to insane levels, like $1000 per 100 crystal. So you have piles of cash for mines, then piles of crystal for infrastructure. Cash also makes you King of the Pirates, which hugely mitigates your poor early military. Really, the black market is the key, even if you're only selling for 200. Losing income due to low infrastructure? Gain it back with the mines you got when you took the planet. You're still better off taking those planets.
Then I rush up the Civ tech for Trade (remember, I'm playing Vasari here, so that's Civ tech 4), and put a trade port in pretty much every system. Even more cash.
It's only then that I bother with military. Mil tech level 2 for Hangers / Missile Frigs, level 1 Supply for a big-enough-for-early-game fleet (at only 9% economy loss, which is ok), level 1 capcrew for a second capship. Get some defences on the frontiers, rely on your early push to have secured enough to justify all-out defense, nab any unowned Terran / Arids nearby, then back to civ tech. (I don't come back to mil tech until I've got all my civ labs built).
Civ tech gets resource upgrades, then rush (!) down the tree to Vasari Jumpgates of Pure Awesome. Suddenly defence gets heaps easier. With judicious pirate attacks you're often not far behind in military even now - all of this is suprisingly fast if you've gone resource-crazy. Then push for Returning Armada, and sit back and get military techs while your fleet goes RAAAH!
I'm in a stupidly-big game at the moment, with 4 hards, 4 mediums, and an easy AI ("the Gimp"). One of each personality type for each group of 4, and I'm right next to the agressive-hard one. I just researched Returning Armada, and I have an economy twice the size of my nearest competitor. I've only just had to fend off the first attacks because, as I said, I own the pirates. What's more, with high development on the map (ie. me), the pirates went to level 3 pretty quick. That hurts early game.
Even on small maps, where admittedly you end up fighting a lot more, a very early, very heavy resource grab can mean plenty of resources to rush defences or re-build fleets. Only against Humans on small maps - who can be relied on to do a decent rush - do you need to focus on military more than resources. Pretty much any other map, it seems to me, resource rush it the way to go - battles are so slow that you almost always have time to get some extra defences going, as long as you have enough income and you weren't completely defenceless to begin with.
*Note that Vasari have tough but expensive frigates. That, IMO, makes them uniquely suited to sitting on a low supply capacity and defending while they tech up - supply really tears up your economy. Sure you can't have as many ships, but you might not have been able to afford to fill a higher supply cap anyway. In terms of cost, you end up with a lot more in the field at the same supply level.
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Tips for fighting the AI (some useful even in all-human games for anti-pirate):
AI fleets largely (completely?) ignore contruction frigates. Keep building cheap-ass defence guns in your system, in range of the enemy (especially siege frigs) but further away than whatever their combats ships are shooting at right now. You can keep a fleet tied up pretty much forever doing this, and with some hangers in the system can often whittle them down.
The AI will also chase Capships all over the system. Jump in, poke 'em, dance around the edge until they get close, jump out. Get to the other side of the jump, turn around and come back, rinse and repeat. If you're using a carrier you'll even be doing some decent damage through all of this.
Put a bounty on two AIs. They'll think it was each other* and start bidding. They lose money, one will get attacked, and then probably the other in the next go 'round, all for a 500 cred investment.
*(Actually, I think they just want to divert the pirates, and see pumping the next-highest bounty as the cheapest way to do that - which makes sense really, but it's easy to manipulate).
I quite like the diplomacy - you need to *earn* your favour, rather than just slowly ask for upgrades / get random fluctuations like most games' "diplomacy". Remember a few things: it doesn't go negative, so if you need a fast ally you can always check what missions are going; losses for failing missions are much less than gains for succeeding, so you don't need to complete every mission; if you're fighting someone, check who else is - they'll have missions for you that you won't have much difficulty doing; getting trade / non-aggression is usually all you need, and that only needs around 60% - two completed missions. Early missions are often just 200 metal or something easy.
Placate your AI neighbours early and you will have heaps of time to get established, and steal those Ice / Molten worlds that the AI takes so long to grab. Better, they'll have to pick someone else to target, which sets up long-term wars that'll go on even if you let your diplomatic rating slip to zero.