If you want to be come a professional, you should do as I said. You also need to take a few classes. You can do it with the Sony a390, but it is a very old camera. If you want to buy lenses for it, you should look at A-Mount lenses.
But I would suggest the if you want to go Pro then you want to be shooting either Nikon or Canon.
Start with the class. Maybe a book about exposure and lighting too.