Off the top of my head, some good essential oils for focus and clarity are lemon and orange – probably most citrus oils, honestly. They help promote a sense of focus and clarity. I’m not much of a tea person myself, but I gathered some tea, incense, and oil recipes from the Witch’s Apothecary lesson that might be helpful for you.
And then @Cosmic_Curiosity created a wonderful post with essential oil blends that you can find here.