Remember not to create your new group if you are going to use the migration tool to move your content! You can create your personal site and become familiar and they work much the same except there are group features.
But the Migration tool WILL create your group for you, and if you create it now manually, you will lock up and not be able to use the same Group ID. You cannot reuse a personal or group ID even if you cancel it. This is so that if you do cancel a personal site or group, no one can come back, use it and appear to be YOU.
So remember - if you are going to MOVE your group content using the Migration tool, do not create your group yet! Just your personal site!