This topic may not seem actionable; however, there are at least two actionable areas from this passage.
When we let sin run its course, as Cain did, the results can be devastating. When you see sin creeping up on you, you need to confront it and stop it in its tracks.
When we spend money to make a purchase, we would like to see our money go as far as possible. Why should this be different with tithes and offerings? We should desire for our money to "get as much of God" as we can (even though, of course, God cannot be bought).