Help with getting gladiator and just overall the game haha

So I'm not new to gaming but man am I new and trash at turn based games. I don't know if there is something that's not clicking or what but it's pretty bad haha. Either way I was checking out the classes and gladiator caught my eye, was considering getting the dlc due to the sale but I know there is no chance I can get through the game to unlock him. Anyone able to lend a hand maybe? Thanks all!