1. A Book of Shadows is a Witch's Journal. The first page you write is 'The Book of Shadows of (Your name)' and the date you started the journal. You write about everything you experience with magick. If you had a successful spell, write it. A grimore is a Witch's Spellbook. These are the spells you create and put in here with testing.
2. Sure, you may have an affinity with a certain type of magick. You are able to tell what you have an affinity for by researching specific types of magick (like elemental magick, candle magick, etc) and seeing what you like or what connects to you. Everyone has an affinity to something, dear :)
3. If you wish to, you may work with a God or a Goddess or both in your magickal workings. You can give offerings to them or put something as tribute to them on your altar. Research various mythologies like Norse Mythology, Egyptian Mythology, or Celtic Mythologies to understand the Gods and Goddesses of them more.
4. Over time, an animal may come to you as your guardian animal. I personally believe they come to you at the right time instead of you to them. There is also your companion animal and your familiar which can be a physical animal as well.
-Regarding Your Beginning in Magick-
You must know your basics before you can spellcast. There are many posts on here about them including that of my own. Practice them everyday until you get a good understanding of them and can perform a technique that deals with one.
I hope I was able to help you.