i recommend watching the series in order it aired: blood and sand, gods of the arena, vengeance and war of the damned. gods of the arena is prequel, and i wouldn’t advise you to skip it, because you’ll have a wider look on the story of batiatus and his ludus and you’ll meet new characters, who are gonna be important for the next seasons.
also, don’t mind the weird cgi in blood and sand. they went for the 300 look at the beginning, but then it’ll look more natural and less odd.
unfortunately, starz had to recast liam mcintyre for the lead role, with andy whitfield’s (the original spartacus) own blessing, as he was fighting non-hodgkin lymphoma. it might take quite some time to get used to liam, but keep in mind that andy and he are different actors with different approach to this character. give him a chance. also the actress for naevia was recast due to lesley-ann brandt’s personal reasons.
rape and sexual assault, abuse, blood, violence, gore, death. please, message me if there’s something more. basically, spartacus is very gore-y and violent show, with lots of sex, cussing, blood and death.