It depends on what you are making. Always mix body safe fragrances together for bath and body(soap) applications. If you are making candles have the appropriate fragrances. Even gel candles take special fragrance oils. That is the main thing to start out with. You can experiment to see what smells good to you. What did you have in mind?
Planning on making a MP using monkey farts FO however, my daughter thinks it should have a banana scent as well and ask about mixing the Monkey Farts with a Banana FO. I have not purchased the Banana FO because I did not if there was a secret to combining them. Both FO's state that they are for soap making.
The description says bananas, berries, bubblegum, and vanilla but I think it smells like real sugary bubble gum...that's why my daughter wants me to add a banana scent.