There really isn't much. If you want to learn about the character, just the first series and the start of the second. Conway's stuff is good.

John Ostrander had a great run with the character: Firestorm vol. 2 #55-56, #58-100 and Annual #5.

Just watch him in The Flash and then Legends

I’ve seen those lol, I want to see more of the character and his villains like killer frost. He has some crazy powers which they underuse in the shows, basically limiting him to fireblasts.

Do you like one firestorm more than the other?

OG Firestorm was 1 of my first favorite heroes, back in the late '70s. But story-wise, definitely read 'DC blackest night' & I also liked the Jason Rusch version, cuz it takes place in Detroit (where I live nearby).