Look at it this way, you don't need Clone Wars or Rebels to like or apreciate Star Wars.
But you do need it to fill in some of the crap they are throwing your way here.
But, yeah mostly re-caps will do:
Ahsoka a pretty decent character created by Lucas and expanded on by Felloni, as once Anakin's apprentice, fated to die with the rest of the Jedi.
Feloni then ridiculously contrived her survival, by introducing some stupid time-portal, so now she can, going-forward, repurpose the legacy mentor role, once meant for Luke.
(who in the Disney-canon, is a complete coward and useless failure), so lucky we have her instead, to do what he failed at.
Ezmo, is some annoying apprentice Jedi who also shouldn't exist through the OT, so Feloni introduced yet another preposterous hyperspace/time/warping space-whales to temporarily "remove" Ezmo from OT continuity (and by extension Thrawn). And will now bring them back just as facile. Seems to be the plot Ahsoka hinges on.
The titular Rebels among others also included the usual clique of repurposed trope characters, including; Sabine, a Mandalorian
& Jedi in training, so pretty much she's the best of everything.
And Hera, pilot of the
Falcon Ghost and now Rebel leader.