This pattern is Intermediate Level
If you are beginner, there are few things you need to know to be successful, and there are lots of YouTube Tutorials that can help you!
How to do a Magic Circle
A basic knowledge of the stitches used
How to increase, how to decrease
Crocheting in the round and keeping track of where round starts with a stitch marker
Keeping track of rounds

The size of your doll will depend on what yarn and needle you use.
I recommend that you make sure the stitches are tight, so that you don’t have fiberfill poking through the stitches. If you see a lot of holes, then go a size down on your crochet hook