Well, since that's where Ahsoka's story starts, I'd highly recommend watching them. Personally, I'd watch them all but it's a lot. From a reddit thread.I’ve seen all the live action stuff but none of the animated. Do I need to watch some of them before Ahsoka?
If you never watched anything from the Clone wars the show is mostly organized in story arcs of 3-4 episodes on average. I assume you just want to watch some episodes with her before she appears in the Mandalorian so I will just put all arcs where she plays a major role
- Season 1 Episode 2 - part of the Malevolence Arc (includes some of her backstory)
- Season 2 Episode 1-3 Cad Bane/Holocron Arc (if no time only watch episode 1 or skip entirely)
- Season 2 Episode 5-8 - Geonosis Arc (she is not in episode 7)
- Season 2 Episode 11 - Lightsaber Lost (skip if no time)
- Season 3 Episode 10 - Heroes on both sides (skip if no time)
- Season 3 Episode 15-17 - Mortis Arc (has a connection to Rebels in case you watched that)
- Season 3 Episode 21-22 - Padawan lost
- Season 4 Episode 14 - A friend in need (skip if not time but it also has Bo Katan in it)
- Season 5 Episode 2-5 - Onderon Arc (she is there the entire time but its not focused on her)
- Season 5 Episode 17-20 - Temple bombing Arc (must watch!)
- Season 7 Episode 5-8 - Ahsoka Arc (most people dont like it but its literally Ahsoka only)
- Season 7 Episode 8-12 - Siege of Mandalore/ Order 66 Arc (must watch!)
Another person put together this Google Doc about what to watch. I would also highly recommend watching all of Rebels, most of the characters in the live-action show come from Rebels.