If you want to clear your mind and think clearly then Basil is very good for this. Juniper berry is also good for stress as are , Cyprus, Mandarin, Geranium, Cedarwood, Marjoram and Patchouli.
Thank you Amethist. I never knew this oils are just couple of mins away from my home. Most of them are available in my city and I will plan to buy them. :facepalm::D
May I ask one more query, how to apply them? In hair? :O_o:
For digestion problems. I frequently get ulcers and throat infection. I have become allergic to this two.