You asked this question a couple of days ago but I didn't see any responses and decided to take a crack at it. So watching the show it looks like it's incredibly inaccurate. So I'll list the most accurate parts I know, as well as the most notable inaccurate ones. Also it should be noted that if you haven't finished the series there are some spoilers for sure.

Accurate Parts:

• The final battle at the end of Season 2 where Spartacus uses vines to escape off Mt. Vesuvius actually happened, believe it or not. Spartacus used the vines to rappel down and outflank the militia.

• The mock gladiatorial games after Crixus is killed did happen. The numbers were roughly correct at 300 men who were forced to fight for the entertainment for the rebels.

• Spartacus dies on the battlefield, like in real life. (Impaled with like 7 spears probably didn't happen), but he was killed in battle. Compared to the movie based on Howard Fast's book where Spartacus survived the final engagement only to be crucified along the Appian Way.

• Gannicus, Crixus, Castus and Oenomaus were the actual leaders of the real revolt. And similar to the show after Mt. Vesuvius Oenomaus is no longer referenced in Appian or Plutarch.

• (I haven't seen the show recently, so I don't remember if this is in it very much) But the rebellion did turn around once they reached northern Italy. Why? Literally no idea and nobody knows either. There are a few schools of thought, but those are educated guesses. But that happened.

• In the real rebellion they were betrayed by the Cilician Pirates as well. Spartacus wanted to sail to Sicily to gain more followers but the pirates were offered more money (or something of more value than what Spartacus offered).

• Crassus was placed in charge of the army after overwhelming defeats of other military units. He did actually bring back the punishment of decimation (where the soldiers drew lots to see who would be killed in groups of 10).

That's the most accurate parts I can think of right now, but I know I'm forgetting some, now onto inaccuracies.

Inaccurate Parts:

• Gannicus was not Celtic but was actually Gallic. In fact, the overwhelming majority of the gladiators at the ludus were Gauls. The rivalry between the Germans and Gauls at the ludus may or may not have happened, but in reality, the two peoples were not fans of each other.

• Gaius Glaber was not buddy-buddy with Batiatus, nor was he in charge of an official legion. He also did not have an intense rivalry with Spartacus specifically. He was in charge of a militia force that was defeated at Vesuvius. Varinius was also dispatched by Rome, and then dispatched by the rebellion.

• In the show Crixus leaves the main force fairly late (correct me if I'm wrong but it's in the last few episodes of season 3). In reality, he left immediately after the winter of 73-72 BCE with a solid chunk of the rebellion at 30,000 people. He was slaughtered, along with his men.

• Castus was a member of the rebellion well before the Cilician Pirates were introduced in the show. He was (possibly) one of the reasons the army turned around in northern Italy.

• Possibly the most glaring inaccuracy is that of Crassus' son. The official knowledge we have of him is hazy at best so the show creators took a lot of liberties with him and turned him into the main villain (in an attempt to understand Crassus and possibly have some viewers side with him).

So those are the glaring inaccuracies with the show, and I know there's way more but those are just the ones I know off the top of my head.

Grey Area Point:

• This last point is heavily debatable and could honestly have gone into either category but it gets its own. You know at the very end where some slaves escape over the horizon? Well, we don't actually know if that happened. It's incredibly plausible, actually very plausible. The rebellion was huge and this could have easily happened, but the thing is we don't really know. There's no written evidence going either way.

So those are the points I could come up with and I know you posted a couple days ago so I'm hoping you're still looking for an answer. Something that was never mentioned in the show is that the main primary source material was written decades after the war. Not to mention the fact it most certainly has a heavy Roman bias, naturally.