>>211520127He's in 3 episodes out of 12, but those are some of the best episodes of the show and season 1 is near-perfect in what it is doing. They fucked up a bit with the finale and season 2 is a rollercoaster of quality, but you can just go watch season 1 for itself, or even just the episodes with Serkis and still get a good story out of it.
If you still need encouragement: you want to see episodes 8-10 (and the literal last 5 minutes of episode 7 to know on what idiotic charges Andor ended up in prison, the scene is actually hilarious)