I have a bit of a dilemma. I ended up with $100 worth of Amazon gift cards, and am looking to spend them on something 40k-related. I could not find Forge World miniatures on Amazon, am mostly caught up on Horus Heresy series, and have way too many miniatures requiring assembly and paint to consider buying more... but after talking with a friend who runs a Black Crusade gaming group (unfortunately rather far away from me), I became interested in buying some of the RPG books from Fantasy Flight Games - Dark Heresy, Deathwatch, Black Crusade, and their innumerable spinoffs and supplements.
So, this is where I would like to ask for community assistance. I am interested in getting some of the RPG source books, but not sure where would be the best place to start. I doubt I will actually get much gaming in (lack of time, no gaming group in the area that I am aware of), so my ideal starting point would be heavy on background/fluff (yet still enough to actually run or participate in a campaign if I were to ever get an opportunity to do so).
From the background/story side of things, I would naturally have interest in power-armored factions (being at B&C and all ), and much less interest in IG/Rogue Traders. The Inquisition would be another interesting area for storyline/campaign theme purposes, and would probably be on my radar.
Since each core rulebook seems to be in the vicinity of $50, it seems that my options would be limited to either two corebooks, or, perhaps, a rulebook, a supplement (or two), and maybe something else. What would you suggest as a good starting point with the $100 budget? Thanks in advance!