When I played Star Ruler I:
* Applied the "Galactic Armory" mod (I think that's the name of it). I don't know how responsible it is for what followed, compared to vanilla.
* Eventually figured out how to build enough defense to get the pirates to leave me alone. Long range artillery was fun.
* Eventually figured out the shipboard industry modules and built some spaceborne factories and thus got around labor costs.
* Then built a really large spaceborne factory that in turn churned out an even larger mobile miner that would gobble up asteroids.
* Then used all those minerals to build a really large spaceborne miner that was also a factory, and went around mining planets.
* Then had that miner/factory build an even larger version of itself, and went around eating planets (not really, but extracting all their minerals in like a half-second pulse of the mammoth mining laser).
* Then (possibly after a few generations, I forget) used my largest miner/factory to build some really gargantuan ships with artillery that could one-shot stars half a galaxy away.
* Entirely coincidentally, my opponents soon had no more stars. I think their planets got lost in the shuffle.
And then I never played the game again. Not that I didn't have fun, but the fun I would have doing it again is below my time-cost threshold, I guess you could say.
But is doing that once worth the price if the game is on a steep sale? Up to you.