There’s this weird cultural norm that says TOS is extremely cheesy, Shatner hams up every episode, the sets are all terrible, and it isn’t worth watching. It’s sad because TOS is my favourite and it has so many interesting stories, and Kirk is such a cool captain. Even TAS is worth a watch, especially the episode Yesteryear!
It’s a real shame TOS got shafted by season 3, and we never got more of its peak due to diminishing budget. That’s what networks love doing though, they can never appreciate a good thing until it’s been off the air for decades and people are clamouring for more.
I would highly recommend anyone starting off with a collection of some of the best or most relevant episodes of TOS, as well as some of the poor ones like Spock’s Brain. I’ve found at least the bad TOS ones are interesting, but bad TNG ones can be just boring.