To prepare for the exam, Cuthbert spent many hours in quiet study.
To get prepared for the exam, Cathy drank a cup of cocoa and put on her extra strong reading glasses.
‘Prepare’ is more passive.
‘Get prepared’ (or get anything) focuses more on the action involved, and on the process, because ‘get’ describes the process of transitioning from not having - to having something.
Here’s another example:
He was drunk - describes his state. Nothing is happening - we just passively hear a description of how he now ‘is’. ie ‘drunk’. He is probably asleep on the staircase, key in hand.
He got drunk - is a whole other story - in fact it IS a story - it alludes to the process of how he got drunk. We might hear of several bars visited, various cocktails imbibed and bartenders met, in that ‘story’ of how he ‘got drunk’.
So neither is wrong - and the one you choose depends on whether you want to ‘describe the current status’ or ‘allude to the process’.
With start, or get started, the ‘get’ provides the impetus for the starting to happen - like a spark that ignites - again, it alludes to the process.
- ‘He started the course’ - passive
- ‘He needed the teachers encouragement to get started’ - impetus to the process starting is provided by the teacher.
- ‘The bike started’
- ‘He kicked down the bike to get it started’
- ‘At last the bike got started - sputtering into life’.