Rosemary and Sesame oil at 0.05%, peppermint oil at 0.04%, thyme and cinnamon oil at 0.03%, garlic oil at 0.02% and an emulsifier such as castille soap, aloe vera gel etc.
Its easiest to put all the oils into a 10ml bottle counting drops as the above %'s then add equal amount of the emulsifier.....shake it all real well ~2-3 minutes then let it sit for a couple hours to make sure it doesn't separate then when ready to mix up with water you'll use 1-2 drops per 8oz water.
If you want it to last longer then you'll want to add vegetable glycerin at 20% soooo 32 oz water x 20% = 6.4oz. Take the 6.4oz vegetable glycerin and add 4-6 drops of the oil mix then add this to 1 quart (32oz) water....stir/shake well and let sit for an hour to ensure it doesn't separate. If it does, shake/mix more
If your on a budget and don't have access to these oils then just go to the garden store or home depot and pick up any essential oil bug mix like Zero Tolerance by Ed Rosenthal, Essential Defense, Dr Earth Final Stop etc