To me C seemed like a show that could have been a really cool shonen-esque show but was kinda ruined by a lack of delving into the ideas behind the concepts and a vastly rushed pace due to the fact that there were only 11 episodes. I mean it was still definitely an okay anime, but the fact that they decided to go the "character-driven story route" rather than the "Pokemon: Wall Street Edition" route pretty much just meant that the very short number of episodes hit them for a double whammy.
In short, it was a nice time filler that I think could have really been a very cool character-driven show if they had of done 24 episodes or so, but with only 11 it isn't much more than just a time waster show to watch when you don't really have something better IMO.
I quite liked C, but probably a bit in the same way that other people like Fate/stay Night; in that it's more about the concept than what it is actually about, plot-wise.
They clearly had a bigger idea of what they wanted to do than what they were given a budget for, and that shows.
But, it's still a cool idea to base an action series around the concept of money. Losing money when you are hit, spending money to do attacks, stealing money from your opponents to increase your own finances and savings, ect. The problem is, as you said, very little of the systems at play beyond the basics are ever explained to the viewer despite them clearly existing, and the show is half the length it should have been.
I first watched it because I saw a clip of it in a random AMV and thought, "Wait, that looked like Persona", and Persona is likely a better comparison than Pokemon to describe it.