You may want to differ between exploration to make some money and sightseeing. For the first you can save some money on some components, e.g. a jump range of 15Ly is perfectly sufficient for the first, if you don't intent to go toooooo far beyond the populated bubble. E.g. if you limit yourself to ~500LY beyond the last habitated system, that opens you to ~8 times the space. And at that distance there is not that much of "fluctuation" in system density. Considering that there are many system in populated space that have not been properly (advanced and detailed) scanned yet, there is not really a reason to go much farther out.
If you want to go sightseeing to specific places far out, like the center of the galaxy, than you may want to maximize your jump range as well; but nebulas, black holes and other interesting objects can also be found much closer.
The Detailed Surface Scanner (~500kcr) is mandatory to maximize your income, but you have to fly more or less close to the bodies to take advantage of it (~1000Ls for the bigger gas giants, down to ~5 Ls for the smallest planets and moons).
The Advanced Discovery Scanner (~1.6Mcr) drastically reduces your time needed per system, as with a single scan it uncovers all bodies in the system - no more parallax scanning or dimishing returns from trips to distant secondary suns without planets.
The fuel scoop allows you to venture beyond habitated space, of course. The better ones (>100k) can save you a lot of time.
With respect to making money - don't expect to get rich very fast. My average in unknown space is ~20k credits per system visited (my max is 120k, but others have earned more already), with maybe an average of ~15 minutes per system to scan most bodies (but not asteroid clusters, and usually also not distant icy planets). To note is, that this ratio should not change/scale much with different ships. So to make millions will usually take days.
I just returned from an ~1 week trip to max ~400LY outside the bubble, scanning ~185 systems that earned me ~3.5 million credits. Considering that I am flying a >10 million Cobra kitted for exploration and combat, also have a T6 and ~8 million credits in the bank before the trip, in the same time I could earn much more with bounty hunting or trading.