I see what you mean. I've tried to keep + buy clumsy/rare b/c I wanted to enable some of the more creative forms of payload (using Reconsider or Deconstruct, for instance, or the Haggle thing), but those are harder to set up, so the difficulty does end up pretty RNG-dependent. I don't want every run to just be "get a bunch of gold and +buy", though. I'll think about what I can do.
Somebody else suggested preventing duplicates in the prep stage, which I'm going to add, so that should make finding different cards easier.