The oils and materials that last the longest are called base notes and generally make up 40-55% of the blend. These are the notes that last longest on the skin as they are the least volatile (take the longest to evaporate). Natural base notes include sandalwood, patchouli, vanilla, vetiver, labdanum and oak moss as well as some of the more exotic materials such as cognac, tobacco, tea and spruce.
The materials that will give your perfume its character are the middle or heart notes, they will be around 20-30% of your finished fragrance concentrate. Heart notes determine the nature of the finished perfume and will pretty much always have floral elements such as rose, jasmine & ylang but could also include spices such as cinnamon or clove and herbal notes such as basil and clary sage.
The final 25-35% of your perfume should be made up of top or head notes. These are the materials that give the first impression of your fragrance but will disappear quite quickly on skin. They are the most volatile and include all the citrus oils as well as spices like nutmeg and black pepper.