I'm a DIYer by nature. If I can make something on my own, I will. I make an all-purpose oil that serves as my preshave (for my head & neck), a beard oil, and an oil cleanser. It's based on the Oil Cleansing Method that is omnipresent on the interwebs.
The thing with a preshave is that it should be emollient enough to serve as a buffer between your skin and the blade, but not so viscous that it clogs your razor. Some guys use coconut oil, neat; but I find I get clogged pores with coconut oil (however good it smells!) I use one part castor oil (extremely viscous) and two parts grapeseed oil (sometimes one part grapeseed and one part almond oil.) I don't add essential oils, though you could (I'd stay away from citrus like lemon or grapefruit as they're irritating and can make the skin photosensitive.)
Good luck on your project.
Cheers!