The exercises you've done so far will help you determine what areas you are good at, and at what times you work best. It is not necessary to specialize, but if you desire to do so, then the more you practice the more you will know of ideas for areas of specialization. Here are some exercise ideas:
1) want to try your hand as an herbal healer? Make infusions of teas and sense what they are doing to you, record physical, psychic, and mental experiences (including taste, smell, etc.) Try easy ones at first; 1 inch piece of ginger root simmered in 1 cup boiling water, or 1 Tablespoon loose cut licorice root simmered in 1 cup of water (slight laxative, look out) Mix up your own incense, try the loose kind that you burn on charcoals first: rosemary, bay, and sage from the cupboard, or cloves and cinnamon, or a small piece of amber perfume resin blended with sandalwood powder, or myrrh, frankincense, copal, and benzoin.
2) Divination is a useful skills that is almost a side effect of knowing your mind and gaining power from within. If Tarot, Runes and Crystals aren't doing if for you, but you still need a tool to go from, try "The Bag of Tricks". I did this when I was little... collect objects from around the house that arouse meaning in you. A toy ring, an earth colored marble, a feather, etc. Use your intuition, the ingredients can change any time you wish to whatever you wish. Put all the objects in a bag, and focus on a person, or have a person draw out an item. Your interpretation for the feather being drawn could be, a flighty person, new found freedom for that person, taking a trip by air soon, etc. a meaning for the ring could be marriage, stuck in a loop, money coming, etc. use your intuition, there are no rules here! Check out the divination section of the Library for more ideas.
3) Try your hand(s) at healing. If a friend has a headache, guide them through "The Little Green Man in My Head" visualization. Have them imagine with you, a little man shoveling their headache, seen as a bright red light", in to a pool of water in their head, where it cools off slowly. Or place one of your hands (your projective hand, usually the one you write or point with) on their forehead and one on the back of their neck. Project energy flowing from one palm to the other. Keep going for a while, then switch hands so that the projective hand in on the back of the neck this time.
4) Kind of a twist on Green Witches, try your skills at gardening or growing plants. See the Plants, Herbs & Spices section of the Library.