I'm still new to this game (although I've played GalCiv I years ago....) but having a blast. What I like about GalCivII is that every game is truely unique. I've started my first game on the biggest map available in Twilight last weekend after having played small and medium maps before and it's awesome...
I'm in the southern tip of the map and the Krynn was bullying me for money, they are the military superpower in the game. At that time I had already conquered the Drengin North of me and culturally assimulated the Drath empire to the Northwest of me (but the Drath still have colonies in the far Northwest of the map). The Krynn empire was in the far north tip of the map together with the Torians and between us from the Western till the Eastern tip were the Korx, Korath Clan and Iconians. As they were so far away I didn't see them as a threat and ignored their increasing demands... then due to a (mega?) event every ship had unlimited range and life support was no longer needed... suddenly I was in reach of their armada and it didn't take all that many turns before the Krynn declared war on me and invaded the former Drengin empire with an impressive amount of fleets....
My old Drengin war veteran ships were no match to them...especially not because the Krynn also found a Arnor Ranger (also the Korath Clan and Iconians had a Ranger.... so 3 rangers in this game) which was cutting through my old ships like a warm knife through butter. I saved the game and thought about my strategy overnight.
The next morning I woke up with a great idea.... I had some money on my account, approx 30k bc and opened a channel with the Korath Clan to see if they wanted to sell me their Ranger, in exchange for some trade goods and about 8k bc they were willing to part with their Ranger! Done deal.... the only problem turned out to be that the Ranger was far away and needed 30 turns to get to the front....
I went into the shipyard and designed a small fighter, luckily I researched the correct weapon line to which the Krynn had no defense, as I had the speed bonus ability I created a small hulled fighter without engine and defense loaded with weapons... my miniaturization was at medium level and my logistics was high enough to fleet 14 of these babies together.
All my production centres started cranking out the new fighters and I've spend my remaining cash on rush buying them. This turned out to be the key... once the Krynn were finally getting close to my main base I had 2 fleets ready and countered there small fleets easily.... replacing my lost fighters with fresh ones on the go... The Krynn had captured the former Drengin homeworld, but I was fighting my way back north, slowly repelling the invaders. I took back the planet and drove the Krynn out of my territory.
During this time my bought Ranger had destroyed the Krynn ranger... unfortunately I lost mine in the battle as well. Funny sidenote is that the Korath Clan surrendered to the Korx 1 turn after I had purchased their Ranger! 
Meanwhile I was flanking a small fleet of transports and fighters to the northwest corner where the Krynn had 2 PQ 20+ planets... needless to say I conquered both two worlds.
The war was going on...and 3,5 years into the war I had developed some large hulled fleet command battleships, loaded with defenses against their missiles and a fleet support module that would give me extra attack power... one of those bundled with my 11 fighters was defeating every Krynn fleet without losses! And I had 3 of such fleets about.... 1 of them progressing north into their territory and the other 2 fleets defending.
Then it happened.... pirate mega event! i love this stuff... pirates everywhere. The only problem... they were using beam weapons and I hadn't researched shield technology. It turned out that my fleets were strong enough to repell the pirates nonetheless. Although I endured some losses, nothing too serious. The Torians and Drath however quickly lost all of their ships and both of them surrendered a few turns after the pirates appeared. The Torians surrendered to the Krynn and the Drath surrendered to me...giving me some nice juicy planets close to the two planets I conquered earlier from the Krynn, so that would be a good point for a new front and production base against the Krynn.
Leaving only me (Terrans), Korx, Iconians and Krynn in the game (as well as the Arcaneans actually...but they only have 2 planets in the far far north east of the map). Before the pirates attacked the Krynn were still about twice as powerful in military rank as me, 2 turns after the pirates I was twice as powerful as them
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And that's where I am now.... I have defeated all the pirate fleets in my territory (but still many out there) and I'm using this quiet period to build up my economy and research more techs.... I'm also preparing to invade the Krynn homeworld as I'm building up forces at the new front that was given to me by my Drath friends. I'm in an alliance with the iconians, but they are not in war with the Krynn, we allied during the war and I cannot get them to attach the Krynn as they have some treaties with them... During the pirate invasion the Korx declared war on the Iconians, so I'm now at war with both the Krynn and Korx... Some interesting future lies ahead of me for this game 