Start with Rubin. Potential outcomes are more grounded and concretely interpretable. The epistemology is simple and won't get in your way, if you're inclined to

Start with Rubin. Potential outcomes are more grounded and concretely interpretable. The epistemology is simple and won't get in your way, if you're inclined to dwell on those things. It also has the huge wealth of well developed techniques. Then move on to Pearl. (btw this is in no way a "standardized" answer, just my opinion about how to start with the basics)