Since there surprisingly didn't seem to be an existing benzene flowchart, I made one that covers the entire progression of the fuel, from when it first becomes available in MV up to Nitrobenzene and the multis unlocked in IV. Note this is for making power; if you want these chemicals for another purpose, this flowchart might not be optimal.
As mentioned, you need lots of wood for benzene, and lots of oxygen and some sulfur for nitrobenzene. The main bottlenecks are nitrogen (pre-multi), Pyros (pre-ICO), fluid extraction (pre-multi), distilling Wood Tar, and making Nitric Acid.
Thanks to C0bra for the templates!