I've been looking but it must be in all the wrong places. The ship and weapons guide in the pinned section has been very helpful but finding a guide devoted to economics and how to progress from early, to mid, to late, to [REDACTED] is sadly absent? I don't need a new user guide though. The tutorials included in the game have been awesome at that.
Are you asking how to make credits, or how to fight [REDACTED]? These don't have to be related (although they can be if you're farming alpha AI cores to boost colony production).
Here's a quick stab at economics:
Late game passive income is all about having set a few colonies at size 6 with 3 profitable industries + commerce + free port, preferably in the same system to share defense fleets. However, getting to that point is a large investment in credits. Also time investment in exploration if you want absolutely highest income possible, but you can often get away with 3 merely OK colonies without any exploration goodies or really amazing resources, and still be pulling in 400,000 passively a month once they're all full size, and you invest about 6 story points in them each (space port + commerce improvements). On the other hand, investment to get to that point can probably hit 10 million credits (3 planets with tier 3 stations alone is 5.25 million credits, and you need those for stability with free port+commerce).
While waiting for colonies to grow, there's a number of ways to make enough credits to support a fleet, although some are more dependent on your combat skills than others.
Easiest ways to make credits without relying on combat:
1) Take a commission with a faction, which provides free credits based on your level monthly. It does come with the downside of potentially hostile core factions.
2) Missions from Galatia Academy can be profitable at the very start with a small fleet (i.e. even just 1 ship). Going from point A to point B in the core worlds for 50 to 100k a pop is good credits at the start, and can quickly let you build up a cheap trade fleet. Many can be done with a single Dram or shuttle. Similarly, intel based exploration missions that say go to X and scan Y, can be done in 1 ship with a lot of fuel capacity. I typically avoid ones which aren't orbiting something obvious or in the heart of the system, just to save time. Collect multiples then just make a grand tour of the locations.
3) Once you've got a couple 100,000 credits, buy a couple transport ships and start buying things cheap and selling them to places that have shortages. For example, go to Eochu Bres, buy drugs for 150 a pop on the black market, hover over the drugs in cargo and hit F1, find a planet in shortage, sell for 500-600 a pop on the black market. A deficit might accept 500-1500 units, so you can make 175k to 525k pretty easily. You can do similar things with other expensive resources. Watch your faction standing though. Doing a mission now and then or killing a bounty to bring up your rep is sometimes necessary.
If you don't want to deal with combat during this phase, just buy up (and restore if needed for max burn and in combat speed) hounds for around 10-15,000 credits each, and throw on Safety Overrides, Unstable Injector, Expanded Cargo holds, and Augmented Drive field. You'll be able to simply disengage from pirates without fighting unless they have some really fast ships, and you can pay off Pathers (who might have SO ships fast enough to catch you) or disengage from them as well. Note, that having other, slower ships than the Hounds with their 255 speed in the fleet may result in having to go through a retreating fight.
4) If there's no obvious trades (which you can find by being in system, and hovering over the item type in question and pressing F1), hit up bars while you have a large amount of unused cargo space and look for trade missions. They scale somewhat with your cargo capacity, and thus have scaling pay as well.
5) Stash good deal (cheap drugs/weapons) and other spare cargo or ships at a colony, or in the abandoned station in Corvus, so as to avoid storage fees.
6) Spending skill points in the industry tree can make the above even more profitable in the form of more cargo/fuel space at tier 1, to more efficient and/or more range at tier 3 (I like the fuel efficiency option for trading). A fleet of 10 hounds with 3 skills in Industry is silly fast with plenty of cargo (1500) for nearly any size shortage, and 90 light year range.
If you've built up millions of credits, found a couple colonies and build them up over time. Earlier is typically better, as income is essentially proportional to planet population.
If you're good at combat method:
1) Do bounties, either bar, contact, or intel bounties that are appropriate for your fleet size. Kill the fleet and don't lose any ships. Simple, right?
Sadly, I often accumulate d-mods doing a pure combat play through, although d-mods doesn't mean the ship becomes useless - just a little bit weaker.
2) Raid pop up pirate/pather bases. Requires investment in marines, but then can get a bunch of resources for cheap (you're essentially trading marines for cargo).
3) Farm <Redacted>, turn in cores for cash to Tri-tach officials, or better yet, put them in your colony industries.
4) Create shortages and surpluses in the core by raiding/shutting down industries with marines, and then selling to the planets now in shortage. Recommend you keep your transponder off for those.