In this gigantic galaxy (DA, dificulty: crippling), I started (Altarian Resistance) with Altaria in the sector at the top of the map (actually the topmost planet of the whole galaxy). Nice corner with only 2 sides to watch, as with any corner .
There was Wisp in the same star system, but the next habitable (by me) planet was 2 sectors away. Habitable planets came 1, rarely 2, per star. When I reached these next star clusters, Krynn was there too. It was fairly hopeless to try to win a colonization race against them, so I looked at the possibility of conquering some of their closest planets...
I noticed they had only built ships with deflectors (shield defences) and no weapons. If I attacked now, I could destroy some of their ships without loss. I started researching planetary invasion and moved my few particle beam (+1 attack, 0 defence) ships towards their planets while monitoring what Krynn was researching.
Jessuins minor race were in the region and I traded stinger tech from them. It turned out that was not necessary so soon: Krynn didn't research space weapons until much later. They kept building deflector-only ships and even researched planetary invasion before space weapons; reminds me of a previous game when I played Krynn and tried to take advantage of their starting trade abilities before researching much weaponry.
Their soldiering ability was therefore low, I had conquered their home planet along with some others before they started building weapons. Apart from a few Yor scouts, the other nearby planets (in the light-blue area in the screenshot) were only occupied by me and Krynn, far away from the other races.
Yor (with their massive range bonus) colonized a planet on the edge of this region and declared war on me, but they couldn't reinforce it easily.
At the screenshot, I had conquered all the planets (except Jessuins) in the region, including Krynn's last planet and the Yor planet. My problems were lack of population so early in the game for loading troop transports, and economy (lack of population, and production spent on building transports); but the other races could send only threats from such a great distance.
The Thalan Empire was clearly dominating the other races. We were both hindered by our economic treaty from near the beginning of the game. Due to the great distance to any other races, I needed a foothold planet somewhere. From what I could see (screenshot; some areas made visible by my survey ships getting there via wormhole), and from other information, Arcean (yellow region) seemed the most likely race to conquer. Luckily for me they surrendered to me before I declared war; they were under attack by the Thalans.
Thalan attitude towards me changed widely throughout the game. I helped their enemies with tech trading and many gifts of ships. Thalan were at war with Korath, the Terrans were in a position to join any side (whoever declared war with an economic treaty?)
The stalemate was disturbed by The Jagged Knife who took over many planets. I spent a long time reconquering some of my own former planets and went into the Thalan region to conquer more, building influence starbases to maximum influence there.
Korath surrendered to me (even my gift ships were wiped out quickly by the Thalans), I defeated the Thalans by influence and invasion, and the Terrans were down to their last 2 planets on the brink of cultural revolt when I won by influence victory after 17 years game time.