Add all essential oils to a glass spray bottle. This is easiest when using a funnel. You can use a mixture of repellent essential oils of your choice, ending up with around 80 drops of essential oils total.
Add the neem oil to your mixture. Neem oil is optional, but also does a great job at keeping mosquitos away. (It does have a rather potent scent, though, so if it bothers you, you can either reduce the amount or leave it out completely.)
Add the alcohol to the bottle. The alcohol is also optional, but it helps to somewhat mix/emulsify the oils into the water mixture. The oils and water will still separate, so you will need to shake the mixture before each use, but it will help dissolve them better each time.
Fill the rest of the (100ml) bottle with distilled water or lavender water. We had just made lavender water with my new distiller this past weekend, so I used that as it's potent fragrance should also help against mosquito bites.
Cap the bottle and shake the mixture before using.
Shake and spray the mixture on your skin before heading outdoors or when in mosquito infested areas. Do not ingest!
Notes
I like to keep a 100ml spray bottle at home, but also fill a travel atomizer, normally used for perfumes, to keep a pocket sized repellent in my purse. You never know when you'll be out at night, so it's always best to be prepared!