I don't play online since my internet really stinks, but I have found that getting the economy up early is very useful (obviously) but I didn't realize just how useful until yesterday when I was playing against a hard AI. Basically, they slaughtered my fleet after I assaulted their homeworld (not realizing that they had massed about 70 ships there), and I realized how weak I was and what a potential threat they were. Then I turned my entire economic might (I had been number 1 in economy the whole time) on frigate production. I replentished my fleet past it's original level of 42 ships in roughly 7 minutes. I clearly still have much to learn....
By the way, great post Ke5trel You clearly worked hard on this.
A strong economy is quite useful in really any strategy game.
I, like you, play pretty much exclusively single-player (even more so since I just got Entrenchment over the weekend, and I'm just getting my feet wet with small maps; Cynosian Rift is one I'm using to test out strategies). I'm finding some sound, basic (and non-faction-specific) strategies that work on small maps:
1. The Fly-in-Aspic Holding Action: This uses a mix of jump inhibitors and hanger-defense bays (which can be further augmented by misslie/beam launchers), which traps any would-be invading fleet like that aforementioned fly in aspic. Throw in the aforementioned missile/beam defense platforms *and* a defensive reaction force of a dozen mixed light and LRM frigates (or better), and the aspic will harden to the thickness of cement.
2. Mixed-fleet attack strategies: There is a reason they are called *fleets*; the mix of ships in a fleet is supposed to be *complimentary*. (All too often, we newbies forget this; I'm as guilty of this error as anyone else.) If you don't have a sufficient screen, even a capital ship can be toasted by nothing more than a frigate-based reaction force. True story - playing as the Vasari against an AI-based TEC on Cynosian Rift, the TEC sent in a battlecruiser with a two-frigate screen against my single planet, which had a dozen light frigates. Worse, I had NO fixed defenses built, such as hanger bays, beam launch stations, etc. So I'm screwed, right? Wrong; despite having nothing more powerful than light frigates, I also had a dozen of them. First the screen, then the cap ship itself, got well and thoroughly smashed. That was a wake-up call (for me); I was bound and determined not to find myself where I had so nastily put the TEC. As opposed to the spam-attack (dozens and dozens of light and/or LRM frigates), or the lightly-screened capital ship, I build real fleets (one capital ship and at least eighteen frigates, with light and LRM frigates in a 2/1 mix; with each capital ship I add, I also add nine frigates AND a light carrier). You can have multiple cap-ships in a fleet (even, perhaps especially in Entrenchment, which adds new cap-ship types to each empire for this purpose); the mix of capital ships can be as important as the mix of frigates. Also, don't forget those cruisers (light carriers are in the cruiser class); some of those cruisers (not just the light carriers) can, when used right, present just the right (and bad-tasting) surprise for the opposition.
3. Research and the attack plan: If you have an attack strategy, what you research (and the order in which you research it) should (in fact, must) compliment the attack strategy. Every item you research has a *budget* (in terms of credits/metal/crystal); just as important is the amount of time each research item "costs", and how many "levels" of time are needed for that item to fully be available. Having something available *when* you need it can be just as critical as having it where you need it, and that is what's critical about the overall research "budget" and how it fits into the attack strategy.
"If you fail to plan, you plan to fail!"