Tea tree essential oil is very popular. Firstly fragrance is really fresh and very nice! It clears the mind from negative thoughts. The aroma of tea tree essential oil as by magic gives you calmness and cheerfulness at the same time. This fragrance blends well with all the other essential oils. So you can experiment safely.
Also tea tree essential oil can be added to 50 ml by 3-4 drops and wipe the face with this mixture. This oil has a drying effect and helps with skin problems.