Don’t learn an accent in character
One of the biggest problems with accents and character voices is that it’s very difficult to disassemble them when they’ve been learnt together. What I mean by this is that if you create a character called “Friendly Scottish Nanny” you might find you have trouble doing a Scottish accent without it sounding like your character or vice versa, you might have trouble creating a friendly nanny without making her Scottish.
Always learn accents outside of a character voice and always try to make a character more than just a voice.
Check out the video below to see what I mean and its pitfalls!