Student or Learner
"Adding food scarcity and expensive fuel to the mix have made for a very volatile situation, he said."
in the text above, does "made for" mean "caused" or "led to"?
how common is it used in informal conversations, please?
Yes, it carries those meanings.
As to how common it is, that's not easy to answer. I've heard the construct, usually in slightly formal or academic contexts.