I'm going to echo everyone else recommending this podcast, it's absolutely incredible non-fiction story telling and it will really deepen your understanding of how we all got to this point in history.

To answer your question, I actually think season 8 (all about the French Commune in 1871 and how external pressures can end up causing liberals and socialists to go to war with each other) is the best one for explaining it, but it will be really confusing if you don't listen to season 7 first (which is all about 1848, when France revolted against a liberal monarchy and most of western Europe went "hey, we should do that too, but differently"), which will be really confusing if you don't listen to season 6 first (all about France 1830, when the liberal monarchy who would be overthrown in 1848 overthrew the absolutist monarchy that came before them) and all its supplemental episodes (all about different western European leaders who would see rebellions in 1848).

Season 3 (all about the French revolution everyone knows about in the 1790s) will help understand a few things going on in 6 and 7, and is also worth listening to just to understand why and how liberalism got going, but I don't think it's strictly necessary to get seasons 6-8, and 3 is ridiculously long season because the French revolution is just an insane series of back and forth plot twists that doesn't let up.

That all said, if you're prepared for something ridiculously long, the final season (all about the Russian revolutions, 1905 and 1917) is an incredibly informative and interesting listen too, and kind of completes the series (this is extremely reductive, but season 1-3 are sort of the "liberalism was a big improvement over what came before it" seasons, 6-8 are sort of the "but liberalism had its problems, which socialism tried to answer" seasons, and 10 is the "but socialism has its problems too" season).

Lastly, it doesn't really touch on the liberalism vs socialism thing, but season 4 (a history of the Haitian revolution that highlights how incredibly destructive racism and colonialism are) is probably the one season I would make everyone in the world listen to if I could.

I highly recommend this podcast. He does a great job of differentiating what the different authors say and what are his own opinions. And he adds corrections to the episode when listeners point out his mistakes. The French, Haitian, 1848, and Russian revolutions really changed how I see the world. Be warned, they can hit dozens of episodes each.

The American and English civil war are OK, not Duncan's fault, it's just the non Anglo revolutions were better material IMO.

I recommend Revolutions too. Mike Duncan is an awesome researcher and writer.