There are actually many combos of essential oils that you can use: lemongrass, citronella, and peppermint all seem to help keep bugs away from you. YL’s Purification has many of these in it.
When I make my spray I use about 3/4 witch hazel base and one quarter filtered water. It takes quite a bit of oil. I use about 15-20 drops and a small bottle like the one pictured. Rosemary and lavender can be really great also. Keep in mind that Melaleuca (or Teatree oil) can be dangerous for cats.
The bottle pictured has rosemary, lemongrass, lavender, and a bit of peppermint. It worked great since I didn’t get any bites…nor did my girls.
I think the key is reapplying often and I even put it in the space around us. The nice part is it smells lovely and it is non-toxic.