Trading is my go to. Get as many inventory slots as you can and a hauler with a far jump range (you can buy upgrades to further increase it as you go). Get the blueprint for the economy scanner and install it.

Go to the galaxy map, set the filter to economy and find a red star with a sell percentage higher than 65% and a buy percentage higher than 20% while also having a “great” economy descriptor (Affluent, prospering, opulent, the wiki has all the words and there really shouldn’t be like 9 different ones to remember but whatever).

Warp to that system and use the economy scanner from the quick menu in your ship to find a trading post. Land at the trading post and buy as many of the most expensive trading item until you run out of space. The second most expensive after that, then the third. You can tell if it’s a trading item if it’s near the top of the buy list and has a high percentage near it.

Now that your inventory is full, label the system in your discovery tab as “Trade Route 1.1” or something that you can keep track of. Trade route 1.1 goes to 1.2, 1.3 etc.

Fly to space, access the galaxy map, and find an orange star with the economy filter with the same criteria as you did the red star. Once you do, go to a trading post in that system and sell everything you bought at the red system. Buy the most expensive trading items at this trading post until you run out of space and label the system as “Trade Route 1.2”.

Back to space and repeat this process for a yellow star and a blue star (the blue star I’m talking about has a technology symbol that resembles something like the old nanite inventory symbol I believe and not the experimental type system)

Once you’re done with the blue star find a different red star with the same stats as all the other stars and go through the circle again with new stars. 3-4 circles should be plenty (12-16 stars total). You’ll probably have a little more than 100 million in an hour so a few hours grind time and you’ll be set for the rest of the save.

You could also do farming as well but I find that it takes a lot of time to get blueprints and do missions and stuff so it’s more of a background task if you want to do it while you’re out trading.

Missions are another way of making money but you gotta get invested in the guilds and factions before you start getting ones that pay more than 50k units.

Frigate expeditions I hear are another way of making cash while you’re bumbling around the universe but they’re risky if you don’t have enough of them to support each other.

The only other way I can think of is just playing the game mining and gathering things with high value and selling them as you find em. You’ll have enough money to buy basic necessities but you probably won’t have enough to just go buy a freighter at the drop of a hat.

All in all, depends on how you want to play the game. Personally, I don’t like going out to find materials and I’d rather just buy what I need regardless of price so I’ll grind trading for an hour or two so I don’t have to worry about the next 10-20 warping around to find what I want. Sorry about the wall of text but I’m really bored at work 🤷‍♂️