Get into a proper shop and have a fitting. Book it up and expect to spend at least an hour being fitted. Nobody can answer the question as everyone's feet are different shapes so what works for one person will be terrible for another.
The boots you end up with will determine the crampons to a degree. Tell the guys in the shop exactly what you want the boots for - it may be that you are better starting with a B2 boot and then getting B3s at a later date once you have more experience.