In all but one of my games, I had no commission, and my only (reliable) variety was whatever I loot from pirates, and maybe one or two ships purchased from Black Market. (Remember that shops often sell clunkers too, so finding a good pristine ship may not be easy.) Early game is the same, kill pirates until I recover a wall of Enforcers, Mules, and Shrike (P)s until I can start smashing 150k+ bounties and/or early expeditions and loot better ships. Also, most ships are clunkers until the end because that is what I loot, and I am not paying an arm-and-a-leg restoring disposable ships. I do not build Heavy Industry and ships until my colony can repel expeditions because HI is an expedition magnet, which means no ship building until the cusp of endgame.
Many non-phase high-tech is TT exclusive but their warships is set to one, making them very rare. The easiest way to get rare high-tech warships is to steal the blueprints from Culann and build the ships yourself. Since Culann is one of the more heavily defended worlds, it is hard to sneak in without a pure phase fleet built for raiding. (They have atrocious capacity, so piling on Additional Berthing to carry more marines is necessary.)
And speaking of phase ships, most factions, including the Independents, have them all, making the likes of Afflictor and Doom common. In my last game, much of my early and midgame was spent raiding New Maxios for all of the phase ships and midline ship blueprints. Independents have a nice selection of things to steal from their undefended world. Luddic Church has Legion, and the Church is also easy to steal from them because most of their patrols hang around Gilead and leave Asher (their industry world) undefended much of the time. Warp in through gas giant next to Asher, smash-and-grab, T-Jump out. Also, the Hegemony industry world in Valhalla is sometimes left undefended and player can get XIV ships and railgun blueprints from them.
I get the most choice by endgame, when I have all the blueprints and can build what I want except Remnant tech (i.e., Sparks).
As for acceptable timeframe for grinding? That varies by person. For me, I cannot binge on games like I used to. Some days, I have no time for games. Even when I do have time, it is often spent on something aside from Starsector.
P.S. What do I enjoy about combat? Being an overpowered avatar of death and quickly and utterly crushing the enemy into fine scrap. (Of course, if my fleet is too strong, they usually run and I auto-resolve for free loot.) I can play fair or even gimp fights, but that is least interesting part of the game. Character has no business fighting hard battles when he can make it easy instead.
Starsector happened to be the first game I played where ships can wield multiple weapons at the same time instead of a forward-facing pea-shooter every other space game I played before. I get to play a big ship with lots of big guns instead of a fighter craft, in theory. It is a reason why I get dismayed over naked hull loadouts where the best loadout is a single gun or two and every other mount empty, like on no-missile Aurora and two plasma Odyssey. Even a unbalanced Conquest with one side with maximum firepower (like two Mjolnir and two needlers) and the other side totally empty is probably more effective than any Conquest with both sides filled or partially filled.