I use repashy superfly, it's full of goodies. I tried some of the small name stuff that's basically potato flakes and yeast, they worked fine, but for a similar price i can buy the repashy product and feel a whole lot more comfortable using it.
I don't make my own because I wouldn't be saving a whole lot of money, and I would be spending a whole lot more time on it. Right now I just fill my electric kettle, hit boil, and prepare 2 large cultures a week. Takes me all of 5 minutes. 2/3 cup of water, 3 tablespoons of media, handful of excelsior, lid. wait 3 hours, dump a bunch of flies in. wait 2 weeks, flies out the bunghole.
If you keep larger darts, bean beetles are just about the cheapest, easiest most prolific food i've ever had the joy of culturing. look into getting some. I don't own any darts, only madagascar reed frogs, and they love the bean beetles. I culture hydei for them, but they like the bean beetles even more.