This is something that I am asked daily.
Candles - I suggest starting at 8% fragrance oil for testing. Some oils are much stronger than others so you may be able to drop this down to 6%, many of my customers do but it is important to test the fragrances one by one and decide the percentage that works best for you and your brand..
Wax melts - Wax melts are typically made using 10% fragrance oil. You can however use more if you wish too and you will find on my website the CLP for 10 & 25% so if you choose to use more then select the correct CLP for your products.