Beginner friendly hills tend to be the ones with good paths, and the ones with good paths tend to be the busy ones
Is it parking issues you are trying to avoid, or busy paths?
What about Ben Vrackie? It'll be busy, but if the car park is full, there's plenty more space in Pitlochry.
Alternatively somewhere in the Ochils like Ben Cleuch or King's Seat Hill, starting from one of the Hillfoots villages.