Compared to all the other games I've played, Vindictus' combat system is unparalleled; I actually feel a sense of engagement with my character. From the MMOs I've experienced, I felt little-to-no combat engagement at all, just clicking some buttons here, holding a key or two to attack and there, you're done. If you can get past a LOT of the flaws surrounding the game which I know is difficult (I've had my fair share of rage-quitting ), Vindictus, in my opinion, is pretty unique.
At this point in time, there's no alternative to making a decent sum of in-game money. Of course, the amount of in-game money someone makes compared to another may seem insignificant depending on the person.
Your best bet for making stable income at this point in time is to farm Season 3 dungeons for the materials (Eg. Godly Cloths, Heavenly Leather, Godly Ore, etc.) that may increase in price for the future smash update where we'll be able to min/max our stats and hoard them.
Doing daily runs such as Rocheste By Sea (Muir) for fast and easy paradise stones (don't forget B/O) and Hero Mode Secret Naughty Chamber (Lv. 50 Succubus) for a small chance at an Enthus ES (valued at 25-30mil) are other alternatives as well.
Farming rings are somewhat worth it depending on the ring itself; if it's a CMA the value is about 60-80 mil but if it's a TR it's around 20-25mil.
If you're looking to make a large sum of money, I currently see no option but if it's a stable income you're looking for, perhaps the method mentioned above will prove useful.