I know Im late to the Bandwagon, but I'm gunna suggest stuff that I (hope that other people have suggested, since u guys are usually better at talking about this stuff) would think would be great lore-wise.
You start out similar to stellaris, but instead of a planet you start similar to Sea of Thieves, only having...let's say a ship similar to fanged fighter. Small, vunerable, etc. However, the last enemy you kill has a treasure map For a rare mineral. These Treasure Maps can be sold at space stations for a quick (but small) reward. Selling them to the station could increase the station's size after you visit 10...20 planets and moons. They got rich off the map, and now they give you better deals for items since YOU were the one that made them rich in the first place.
However, keeping the map will allow you to do a side-quest of sorts. The end could include a ghost ship of sorts, maybe protecting the treasure, but it's a boss. A Deadly Boss. The reward would be quite plentiful, allowing you to buy upgrades to the ship, buying new ships, etc. HOWEVER, only 3 of these maps can be found in the game campaign once you start.
Anyways, once you conquer a planet (whether it be populated or not, forced or peaceful takeover) You will get a transmission from a nearby faction. You will most likely not have a high reputation in the galaxy yet, so they will not take you very seriously for a threat. You will most likely be prompted to join them, or fight them. Joining them means you lose your ship, but you get a boost in reputation, maybe even get more credits. Fighting them also gains reputation, but in different ways. Other factions will also notice you, but take you more seriously. However, fighting the faction gives you Bad rep. You gain nicknames, bounties on you, etc. Moreover, stations in their territory will not sell to you, unless bribed or convinced.
Anyways, thought I might talk about some lore-related ideas.
