This mission was tricky. But it is doable. I started off with 100% spending since you start with 30k of money.
I restarted game several times (crtl+N) until i had some nice bonus tiles, onne of which was the Precursor mine (+700% prod) on my capital planet (woohooo)

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I had 2 planets with research focus and the main doing prod. I colonised a new planet, and i was doing ok, but the DL soon came and took that planet with 10 soldiers vs 3000 pop

I couldnt kill a single soldier!! agggg ... So i reloaded the last turn and abandoned the planet. My allies soon launched colonizers and battled the DL for it lol
A fighter with 20 atak (masss drivers) soon appeared and kiled a ship or two of mine, and proceeded to kill the an Economic starbase I had. I recalled my fighters and stacked them with about 10-15 atak. I went back and kiled the DL ship. But the main thing that saved me was researching heavily into ARMOR, and building a military starbase with all atak and defence bonuses i had at the time. I lost some ships but destroyed the small fighters they sent me.
Then heavy fighters with 40 atak MDs showed up. I had a nice enough defense to keep them away. I just kept reaserching + social building + churning out fighters and then upgrading existing ones, till i was able to take down the 40MD fighters. I built better ships and upgraded Armor and upgraded my starbase. I never colonized another planet cause it would spread me too thin.
When i felt i was safe in my area, a Dreadnaught appeared with 60 MD atack and around 70 HP

Forunately with the starbase beefing me up and having 2-3 stacked fleets, the DD did not come close.
I kept reaserching into Weapons / Armor / Engines / Logistics mainly. Also I always trades techs with my allies. My money was getting low kinda fast but I kept 100% funding all the time (till very late on the game). I also discovered that I needed a lot more range to get the Drengin HW (or some plantes/bases on the way). so i did soem reaserch into Range (life support).
Needless to say, I got all my breaks from my allies (the Arceans) who were doing good on researching.
I traded them for the medium scale building (which then i contrinued researching to large scale building), and then I traded them for a MD weapon they just researched (+7 atack MD).
And that was it. I made a Large ship with 60+ MD atak and put it in a small fleet. This beast ate up about everything in its way. I had to kill a few things to get more lvls on my ships to atak the dreadnaught (which is very dam powerful btw esp that it had picked up a few lvls by that time).
I ended annihilating everythign and everyone (Except my allies of course). Late in the game, when I ran into negative funds, I started to sell techs to my allies until they ran out of money. Anomolies helped with +1000bc abd +2500 bcs. I lowered funding later on, made some constructors, built a few garded bases, and sent some Troops and conquered the Yors and then the Drengins.
Even without the powerful MD gun i got, I had good enough firepower, because I had lots of ships and I researched a lot in Weapons.
So in short, it is doable.
- Get some good bonus tiles at start.
- Go full 100% spending.
- Research Armor / Weapons / Engines / Logistics mainly.
- Trade techs with your allies when they have something (give them your lower techs and see if they can add money on top of the deal lol).
- build a military starbase around your starting area but farther down so its not an easy picking.
- build small fighter fleets and stak them with latest weapons + armor (vs Mass Drivers).
- build bases to get to the far away places (plus some research into range/life support).
- get all the anomolies you can, and then park your Scount ship infront of your planet to give you a nice early warning.
thats all i remember lol good luck