Presumably, you prob want to watch some of the animations if you want to get Ashoka, or at least read some synopsis for both Clone wars and Rebels. Ashoka's character is almost entirely built in the former and that person she is looking for in the Mandalorian? Pretty sure that is Erza, basically the Rebels protagonist.
As for Andor, I dunno, felt pretty underpromoted to me. He is a way to obscure character for the casual viewer to go "It's Star Wars, we basically have to watch it"